#### Question

In a ΔABC, if AB = AC and ∠B = 70°, find ∠A.

#### Solution

Consider , ΔABC we have `∠B=70^@` and AB =AC

Since, AB A C ABC is an isosceles triangle

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

⇒`∠B = ∠C = 70^@`

And also,

Sum of angles in a triangle `180^@`

⇒ `∠A+∠B+∠C=180^@`

⇒`∠A+70^@+70^@=180^@`

⇒`∠A+140^@=180^@`

⇒`∠A=180^@-140^@⇒∠A=40^@`

Is there an error in this question or solution?

Solution In a δAbc, If Ab = Ac and ∠B = 70°, Find ∠A. Concept: Congruence of Triangles.