Two complementary angles are in the ratio 4 : 5. Find the angles.

Let angles be (4x)° and (5x)°

Complementary angles sum = 90°

∴ 4x° + 5x° = 90°

⇒ 9x° = 90°

⇒ x° = $\dfrac{90^{\circ}}{9}$

⇒ x° = 10°

Angles:

(4x)° = (4 x 10)° = 40°

(5x)° = (5 x 10)° = 50°

Hence, the required angles are 40° and 50°.