Act Math Practice

Plane Geometry Answer 5

Plane Geometry Answer 5:

5. Consider the isosceles triangle in the diagram below:

What is the measurement of ÐB ?

A. 36°

B. 45°

C. 72°

D. 144°

E. Cannot be determined from the information provided.

The correct answer is C.

Remember these concepts:

The sum of all three angles in a triangle is always 180°.

Two sides of an isosceles triangle are equal in length, and their corresponding angles are also equal.

So, we need to deduct the degrees given from 180° to find out the total degrees of the two other angles:

180° - 36° = 144°

Now divide this result by two in order to find out how many degree each angle has:

144° ÷ 2 = 72°

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