Question

In a $\Delta ABC$, if $\angle A=\angle B+\angle C,$ then $\angle A=$ ..........

• A. ${60}^{\circ }$
• B. ${45}^{\circ }$
• C. ${90}^{\circ }$
• D. none

Answer 1

The correct option is C ${90}^{\circ }$

We have,
$\angle A+\angle B+\angle C={180}^{\circ }$
$(\angle B+\angle C)+(\angle B+\angle C)={180}^{\circ }$
$2(\angle B+\angle C)={180}^{\circ }$
$\angle B+\angle C={90}^o$
So $\angle A={90}^o$