Question

In triangle ABC if AB=BC and angle B = 70 degree angle A will be

Answer 1

Answer:

Angle A = 55°

Step-by-step explanation:

In triangle ABC,

AB = BC

Therefore, triangle ABC is an isosceles triangle.

Therefore, Angle C = Angle A.... ( Angle opposite

to equal sides of an isosceles

triangle are equal )

Angle A + Angle B + Angle C = 180°.....( Sum of

measure of all angles of a

triangle is 180° )

Angle A + 70° + Angle A= 180°

2*Angle A + 70° = 180°

2*Angle A = 180° - 70°

Angle A = 110° / 2

Therefore, Angle A = 55°

Answer 2

Angle A is $40^{o}$.

Step-by-step explanation:

Given:

The given triangle is Δ$ABC$ is given below and $AB=BC$ and ∠$B=70^{o}$

To find: ∠$A$

Solution:

Since $AB=BC$, the triangle is an isosceles triangle.

An isosceles triangle has two equal sides which also means that the angles opposite to these sides will also be equal.

From the figure,

∠$B=$∠$C=70^{o}$

It is known that sum of angles of triangle is $180^{o}$.

So,

∠$A+$∠$B+$∠$C=180^{o}$

$x+70^{o} +70^{o} =180^{o}\\x=40^{o}$

So, ∠$A=x=40^{o}$