Question

Find the approximate value of $\angle$A in $\Delta ABC$ if $\angle A=\angle B=2\angle C.$

• A. ${70}^o$
• B. ${72}^o$
• C. ${81}^o$
• D. ${85}^o$

Answer 1

The correct option is B ${72}^o$

We know that

Sum of all angle of triangle is ${180}^o$

Then $\angle A+\angle B+\angle C=180$

Given $\angle A=\angle B=2\angle C$

Then $\angle C=\frac{1}{2}\angle A=\frac{1}{2}\angle B$

$\therefore \angle A+\angle A+\frac{1}{2}\angle A=180$

$\Rightarrow \frac{5}{2}\angle A=180$

$\Rightarrow \angle A={72}^o$