Question

In ∆ABC, AB = AC , ∠A = 5y + 20° and each base angle is 2 /5 th of the ∠A . Find ∠A .​

Answer 1

Answer:

∠A = 100°

Step-by-step explanation:

Since AB = AC

∴∠B = ∠C  [Angles opposite to equal sides are also equal]

Accrding to question ∠B = ∠C = (2/5)∠A ---- (i)

Also, ∠A + ∠B + ∠C = 180° [Angle Sum Property of Triangle]

Putting values of ∠B and ∠C from eq.(i)

$\angle A +\frac{2}{5}\angle A+\frac{2}{5}\angle A=180^o$

$\frac{9}{5}\angle A=180^o$

$\angle A=180^o \times \frac{5}{9}$

$\angle A = 100$

Hence, ∠A = 100°

No need for information ∠A = 5y + 20°, to find ∠A