Question

graded quiz: polygons and triangles
question 3 (5 points)
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if triangle abc is isosceles, what is the value of ∠a?

Explanation:

Step1: Use the property of isosceles triangle

In an isosceles triangle \(ABC\), if \(AB = AC\), then \(\angle B=\angle C = 51^{\circ}\)

Step2: Use the angle - sum property of a triangle

The sum of interior angles of a triangle is \(180^{\circ}\). Let \(\angle A=x\). Then \(x + 51^{\circ}+51^{\circ}=180^{\circ}\)

$$x=180^{\circ}-(51^{\circ}+ 51^{\circ})$$

$$x = 180^{\circ}-102^{\circ}$$

$$x = 78^{\circ}$$

Answer:

\(78^{\circ}\)