In a triangle ABC, the angle is c = 90 degrees, AB = 20cm, CB = 16cm. find cosA.

Given:
ABC triangle is rectangular;
∡ С = 90 °;
Hypotenuse AB = 20 cm;
BC leg = 16 cm;
Find: cos (∡ A).
Decision:
The cosine of the angle A of a right triangle is the ratio of the leg to the hypotenuse.
cos (∡ A) = BC / AB = 16 cm / 20 cm = 16/20 = 4/5 = 0.8;
Hence, we obtain cos (∡ A) = 0.8.
Answer: cos (∡ A) = 0.8.