# If angle A has a measurement of 42° and is complementary to angle B, what's the measure of angle B?

138°, 48°, 38°, 42°

**Solution:**

Two angles are complementary angles when they sum up to 90°.

If angle A and B are complementary angles, then

A + B = 90°

A = 42°

Substituting the value we get

42° + B = 90°

By further calculation

B = 90° - 42° = 48°

Therefore, the measure of angle B is 48°.

## If angle A has a measurement of 42° and is complementary to angle B, what's the measure of angle B?

138°, 48°, 38°, 42°

**Summary:**

If angle A has a measurement of 42° and is complementary to angle B, the measure of angle B is 48°.