g the following
substitution,
<math display="block" xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mtable><mtr><mtd columnalign="right" style="text-align: right; padding-right: 0"><msup><mi>τ</mi><mn>2</mn></msup></mtd><mtd columnalign="left" style="text-align: left; padding-left: 0"><mo>=</mo><msubsup><mi>τ</mi><mi>b</mi><mn>2</mn></msubsup><mo>+</mo><msubsup><mi>τ</mi><mi>w</mi><mn>2</mn></msubsup><mo>,</mo></mtd></mtr><mtr><mtd columnalign="right" style="text-align: right; padding-right: 0"><m