<div class="_markdown_404681">
  <p>
    #text "Einstein wrote "
    <span class="katex">
      <span class="katex-mathml">
        <math xmlns="http://www.w3.org/1998/Math/MathML">
          <semantics>
            <mrow>
              <mi>
                #text "E"
              <mo>
                #text "="
              <mi>
                #text "m"
              <msup>
                <mi>
                  #text "c"
                <mn>
                  #text "2"
            <annotation encoding="application/x-tex">
              #text "E = mc^2"
      <span aria-hidden="true" class="katex-html">
        <span class="base">
          <span class="strut" style="height: 0.6833em;">
          <span class="mord mathnormal" style="margin-right: 0.0576em;">
            #text "E"
          <span class="mspace" style="margin-right: 0.2778em;">
          <span class="mrel">
            #text "="
          <span class="mspace" style="margin-right: 0.2778em;">
        <span class="base">
          <span class="strut" style="height: 0.8141em;">
          <span class="mord mathnormal">
            #text "m"
          <span class="mord">
            <span class="mord mathnormal">
              #text "c"
            <span class="msupsub">
              <span class="vlist-t">
                <span class="vlist-r">
                  <span class="vlist" style="height: 0.8141em;">
                    <span style="top: -3.063em; margin-right: 0.05em;">
                      <span class="pstrut" style="height: 2.7em;">
                      <span class="sizing reset-size6 size3 mtight">
                        <span class="mord mtight">
                          #text "2"
    #text " inline."
  <span class="katex-display">
    <span class="katex">
      <span class="katex-mathml">
        <math display="block" xmlns="http://www.w3.org/1998/Math/MathML">
          <semantics>
            <mrow>
              <mfrac>
                <mrow>
                  <mi mathvariant="normal">
                    #text "∂"
                  <mi mathvariant="bold">
                    #text "u"
                <mrow>
                  <mi mathvariant="normal">
                    #text "∂"
                  <mi>
                    #text "t"
              <mo>
                #text "+"
              <mo stretchy="false">
                #text "("
              <mi mathvariant="bold">
                #text "u"
              <mo>
                #text "⋅"
              <mi mathvariant="normal">
                #text "∇"
              <mo stretchy="false">
                #text ")"
              <mi mathvariant="bold">
                #text "u"
              <mo>
                #text "="
              <mo>
                #text "−"
              <mfrac>
                <mn>
                  #text "1"
                <mi>
                  #text "ρ"
              <mi mathvariant="normal">
                #text "∇"
              <mi>
                #text "p"
            <annotation encoding="application/x-tex">
              #text "\\frac{\\partial \\mathbf{u}}{\\partial t} + (\\mathbf{u} \\cdot \\nabla)\\mathbf{u} = -\\frac{1}{\\rho}\\nabla p"
      <span aria-hidden="true" class="katex-html">
        <span class="base">
          <span class="strut" style="height: 2.0574em; vertical-align: -0.686em;">
          <span class="mord">
            <span class="mopen nulldelimiter">
            <span class="mfrac">
              <span class="vlist-t vlist-t2">
                <span class="vlist-r">
                  <span class="vlist" style="height: 1.3714em;">
                    <span style="top: -2.314em;">
                      <span class="pstrut" style="height: 3em;">
                      <span class="mord">
                        <span class="mord" style="margin-right: 0.0556em;">
                          #text "∂"
                        <span class="mord mathnormal">
                          #text "t"
                    <span style="top: -3.23em;">
                      <span class="pstrut" style="height: 3em;">
                      <span class="frac-line" style="border-bottom-width: 0.04em;">
                    <span style="top: -3.677em;">
                      <span class="pstrut" style="height: 3em;">
                      <span class="mord">
                        <span class="mord" style="margin-right: 0.0556em;">
                          #text "∂"
                        <span class="mord mathbf">
                          #text "u"
                  <span class="vlist-s">
                    #text "​"
                <span class="vlist-r">
                  <span class="vlist" style="height: 0.686em;">
                    <span>
            <span class="mclose nulldelimiter">
          <span class="mspace" style="margin-right: 0.2222em;">
          <span class="mbin">
            #text "+"
          <span class="mspace" style="margin-right: 0.2222em;">
        <span class="base">
          <span class="strut" style="height: 1em; vertical-align: -0.25em;">
          <span class="mopen">
            #text "("
          <span class="mord mathbf">
            #text "u"
          <span class="mspace" style="margin-right: 0.2222em;">
          <span class="mbin">
            #text "⋅"
          <span class="mspace" style="margin-right: 0.2222em;">
        <span class="base">
          <span class="strut" style="height: 1em; vertical-align: -0.25em;">
          <span class="mord">
            #text "∇"
          <span class="mclose">
            #text ")"
          <span class="mord mathbf">
            #text "u"
          <span class="mspace" style="margin-right: 0.2778em;">
          <span class="mrel">
            #text "="
          <span class="mspace" style="margin-right: 0.2778em;">
        <span class="base">
          <span class="strut" style="height: 2.2019em; vertical-align: -0.8804em;">
          <span class="mord">
            #text "−"
          <span class="mord">
            <span class="mopen nulldelimiter">
            <span class="mfrac">
              <span class="vlist-t vlist-t2">
                <span class="vlist-r">
                  <span class="vlist" style="height: 1.3214em;">
                    <span style="top: -2.314em;">
                      <span class="pstrut" style="height: 3em;">
                      <span class="mord">
                        <span class="mord mathnormal">
                          #text "ρ"
                    <span style="top: -3.23em;">
                      <span class="pstrut" style="height: 3em;">
                      <span class="frac-line" style="border-bottom-width: 0.04em;">
                    <span style="top: -3.677em;">
                      <span class="pstrut" style="height: 3em;">
                      <span class="mord">
                        <span class="mord">
                          #text "1"
                  <span class="vlist-s">
                    #text "​"
                <span class="vlist-r">
                  <span class="vlist" style="height: 0.8804em;">
                    <span>
            <span class="mclose nulldelimiter">
          <span class="mord">
            #text "∇"
          <span class="mord mathnormal">
            #text "p"
  <p>
    #text "Backslash inline "
    <span class="katex">
      <span class="katex-mathml">
        <math xmlns="http://www.w3.org/1998/Math/MathML">
          <semantics>
            <mrow>
              <mfrac>
                <mn>
                  #text "1"
                <mn>
                  #text "5"
            <annotation encoding="application/x-tex">
              #text "\\frac{1}{5}"
      <span aria-hidden="true" class="katex-html">
        <span class="base">
          <span class="strut" style="height: 1.1901em; vertical-align: -0.345em;">
          <span class="mord">
            <span class="mopen nulldelimiter">
            <span class="mfrac">
              <span class="vlist-t vlist-t2">
                <span class="vlist-r">
                  <span class="vlist" style="height: 0.8451em;">
                    <span style="top: -2.655em;">
                      <span class="pstrut" style="height: 3em;">
                      <span class="sizing reset-size6 size3 mtight">
                        <span class="mord mtight">
                          <span class="mord mtight">
                            #text "5"
                    <span style="top: -3.23em;">
                      <span class="pstrut" style="height: 3em;">
                      <span class="frac-line" style="border-bottom-width: 0.04em;">
                    <span style="top: -3.394em;">
                      <span class="pstrut" style="height: 3em;">
                      <span class="sizing reset-size6 size3 mtight">
                        <span class="mord mtight">
                          <span class="mord mtight">
                            #text "1"
                  <span class="vlist-s">
                    #text "​"
                <span class="vlist-r">
                  <span class="vlist" style="height: 0.345em;">
                    <span>
            <span class="mclose nulldelimiter">
    #text " and display:"
  <span class="katex-display">
    <span class="katex">
      <span class="katex-mathml">
        <math display="block" xmlns="http://www.w3.org/1998/Math/MathML">
          <semantics>
            <mrow>
              <mfrac>
                <mi>
                  #text "π"
                <mn>
                  #text "4"
              <mo>
                #text "<"
              <mi>
                #text "θ"
              <mo>
                #text "<"
              <mfrac>
                <mi>
                  #text "π"
                <mn>
                  #text "2"
            <annotation encoding="application/x-tex">
              #text "\\frac{\\pi}{4} < \\theta < \\frac{\\pi}{2}"
      <span aria-hidden="true" class="katex-html">
        <span class="base">
          <span class="strut" style="height: 1.7936em; vertical-align: -0.686em;">
          <span class="mord">
            <span class="mopen nulldelimiter">
            <span class="mfrac">
              <span class="vlist-t vlist-t2">
                <span class="vlist-r">
                  <span class="vlist" style="height: 1.1076em;">
                    <span style="top: -2.314em;">
                      <span class="pstrut" style="height: 3em;">
                      <span class="mord">
                        <span class="mord">
                          #text "4"
                    <span style="top: -3.23em;">
                      <span class="pstrut" style="height: 3em;">
                      <span class="frac-line" style="border-bottom-width: 0.04em;">
                    <span style="top: -3.677em;">
                      <span class="pstrut" style="height: 3em;">
                      <span class="mord">
                        <span class="mord mathnormal" style="margin-right: 0.0359em;">
                          #text "π"
                  <span class="vlist-s">
                    #text "​"
                <span class="vlist-r">
                  <span class="vlist" style="height: 0.686em;">
                    <span>
            <span class="mclose nulldelimiter">
          <span class="mspace" style="margin-right: 0.2778em;">
          <span class="mrel">
            #text "<"
          <span class="mspace" style="margin-right: 0.2778em;">
        <span class="base">
          <span class="strut" style="height: 0.7335em; vertical-align: -0.0391em;">
          <span class="mord mathnormal" style="margin-right: 0.0278em;">
            #text "θ"
          <span class="mspace" style="margin-right: 0.2778em;">
          <span class="mrel">
            #text "<"
          <span class="mspace" style="margin-right: 0.2778em;">
        <span class="base">
          <span class="strut" style="height: 1.7936em; vertical-align: -0.686em;">
          <span class="mord">
            <span class="mopen nulldelimiter">
            <span class="mfrac">
              <span class="vlist-t vlist-t2">
                <span class="vlist-r">
                  <span class="vlist" style="height: 1.1076em;">
                    <span style="top: -2.314em;">
                      <span class="pstrut" style="height: 3em;">
                      <span class="mord">
                        <span class="mord">
                          #text "2"
                    <span style="top: -3.23em;">
                      <span class="pstrut" style="height: 3em;">
                      <span class="frac-line" style="border-bottom-width: 0.04em;">
                    <span style="top: -3.677em;">
                      <span class="pstrut" style="height: 3em;">
                      <span class="mord">
                        <span class="mord mathnormal" style="margin-right: 0.0359em;">
                          #text "π"
                  <span class="vlist-s">
                    #text "​"
                <span class="vlist-r">
                  <span class="vlist" style="height: 0.686em;">
                    <span>
            <span class="mclose nulldelimiter">
