In triangle ABC, angle C = 90, cos A = 0.4. Find sin A.

In triangle ABC, the angle C = 90 ° and cos A = 0.4 are known.

Find sin A.

In order to find sin a, we apply the trigonometry formula.

sin ^ 2 a + cos ^ 2 a = 1;

Substitute the known values into the identity and find sin a.

sin ^ 2 a + 0.4 ^ 2 = 1;

sin ^ 2 a + 0.16 = 1;

sin ^ 2 a = 1 – 0.16;

sin ^ 2 a = 0.84;

sin a = √0.84;

sin a = 2√0.21.

Answer: sin a = 2√0.21.