Why (90⁰-θ)?
- Thread starter Indranil
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The sum of the interior angles in a triangle is \(\displaystyle 180^{\circ}\). So, given those two angles, let's call the third \(\displaystyle \beta\). Hence:
\(\displaystyle 90^{\circ}+\theta+\beta=180^{\circ}\)
Subtract \(\displaystyle 90^{\circ}+\theta\) from both sides:
\(\displaystyle \beta=180^{\circ}-(90^{\circ}+\theta)=90^{\circ}-\theta\)
\(\displaystyle 90^{\circ}+\theta+\beta=180^{\circ}\)
Subtract \(\displaystyle 90^{\circ}+\theta\) from both sides:
\(\displaystyle \beta=180^{\circ}-(90^{\circ}+\theta)=90^{\circ}-\theta\)