Equilateral and Isosceles Triangles

If an Isosceles triangle has two BASE angles that are 76°. Then what is the measure of the vertex angle? Label unknown angle as x. #10

HINT: DRAW AND LABEL YOUR TRIANGLE AND USE THE TRIANGLE SUM THEOREM TO SOLVE FOR THE MISSING VERTEX ANGLE.

Find x if Triangle ABC is an equilateral triangle (all sides are equal and all angles are 60 degrees). #11

• 2

• 4

• 6

• 8

Which sides are congruent?

• AB and AC

• AB and BC

• AC and BC

• ABC and ACB

CAB and ΔCTB are isosceles.

m ∠CTB = 87º and m ∠CAB = 65º.

Find m ∠ACT. #15

• 46.5º

• 104º

• 57.5º

• 115º

ΔGAB is isosceles. The exterior angle at point B measures 138º.

Find m∠A. #17

ΔBUG is isosceles. m ∠B = x + 10m ∠U = 3x

Find m ∠U. #18

Find the value of x. #19

• 7

• 60

• 8

• -4

Select the letter that represents a right isosceles triangle. #21

• A

• B

• C

• D

Find the value of x. #23

• 180

• 57

• 61.5

• 32.7

Solve for the value of x. #24

• 7

• 9

• 10

• -11