Question

Find the measure of the missing angle.
77°

Answer 1

Answer: The missing angle is 13°

Explanation:

Let ∠B

be the missing angle.

Let ∠A

be the angle that measures

77∘Let ∠C

the right angle that measures

90∘

The following is true of all triangles:

∠A+∠B+∠C=180∘

Express the above equation as

∠B

in terms of the other angles:

∠B=180∘−∠A−∠C

Substitute the values for ∠A and ∠C

∠B=180∘−77∘−90∘

∠B=13∘