Question

In ∆ABC, angle A = 70°.
If AB=AC, then the measure of angle B is

Options

1 - 45°
2 - 50°
3 - 55°
4 - 110°
​

Answer 1

Given :-

➝AB =AC

➝∠A = 70 °

To find :-

$\blue{Measure \: of \: \angle B}$

Solution :-

∵ Two sides of triangle are equal, we say that ∆ABC is isosceles triangle.

Hence by the property of isosceles triangle, we know that base angles are also equal.

∴ ∠B = ∠C ___ (1)

$\boxed{\bold{∠B = ∠C}}$

Now,

Sum of all angles in any triangle = 180°

∴ ∠A + ∠B + ∠C = 180°

⇒ 70° + ∠B + ∠C = 180°

⇒ 2 ∠B = 180° - 70° ____ from (1)

⇒ 2∠B= 110°

⇒ ∠B = 55°

$\boxed{\bold{∠B = 55°}}$

∴ Correct option ↠ 3

_________༒__________

Answer 2

Step-by-step explanation:

Solution:-

Since, AB = AC, therefore, ∠B=∠C

By angle sum property of triangle,

-----> ∠A+∠B+∠C=180

----->70 °+2∠B=180

----->2∠B=110 °

----->∠B=55 °

Hence, ∠B=∠C=55

Hope this helps you ✍️