Question

In $\Delta$ABC, $\angle$B = 50${}^{\circ }$. Find $\angle$A, if $\angle$B is congruent to $\angle$C.

• A. 100${}^{\circ }$
• B. 50${}^{\circ }$
• C. 80${}^{\circ }$
• D. 90${}^{\circ }$

Answer 1

The correct option is C

80${}^{\circ }$

Since $\angle$C is congruent to $\angle$B, $\angle$C = 50${}^{\circ }$.

Sum of the angles of a triangle = 180${}^{\circ }$.

So, $\angle$A + $\angle$B + $\angle$C = 180${}^{\circ }$

$\angle$A = 180${}^{\circ }$– (50${}^{\circ }$ + 50${}^{\circ }$)
= 180${}^{\circ }$ – 100${}^{\circ }$
= 80${}^{\circ }$