Question

Consider the figure:

If BC = AC, x = 2y, and angle ∠ACB = 60^o, then find the value of ∠B + y (in degrees).

___

Answer 1

$\angle$C = ${60}^{\circ }$​ and BC = AC,
By angle sum property of triangle, $\angle$A = $\angle$B = ${60}^{\circ }$​

$\angle$A + $\angle$B + x + y = ${60}^{\circ }$​ + ${60}^{\circ }$​ + ${120}^{\circ }$​ = ${240}^{\circ }$​
=>y + 2y = ${120}^{\circ }$​ => y = ${40}^{\circ }$​

Hence, $\angle$B + y = ${100}^{\circ }$​