Question

Find the interior angles of a right-angled isosceles triangle.

• A. ${30}^o$
• B. ${45}^o$
• C. ${60}^o$
• D. ${90}^o$

Answer 1

Answer: (B), (D)

${90}^o$

A right-angled triangle has one interior angle of ${90}^o.$

From the property of sum of interior angles is ${180}^o,$ the sum of other two angles of a right-angled triangle should be ${180}^o-{90}^o={90}^o.$

Also, for an isosceles triangle, two angles are equal in measure, say $\angle a.$

$\therefore \angle a+\angle a={90}^o$
$\Rightarrow \angle a=\frac{{90}^o}{2}={45}^o$

Hence, the interior angles are ${45}^o,{45}^o$ and ${90}^o.$