Question

In $\Delta$ ABC; AB =AC and $\angle$ A : \angle B \) = 8: 5; find angle A.

Answer 1

Given ,

ab = ac

$\angle b:\angle b=8:5$

let them be 8x , 5x


$\angle b=\angle c$

angles opposite to equal sides are equal

now

$\angle a+\angle b+\angle c={180}^0$

8x + 5x + 5x = 180

18x = 180

x = 10

now $\angle a=8x={80}^0$