Question

Sina×tga=1/2, cosa=?​

Answer 1

cos a = -1.28 and 0.78

Explanation:

The question is not properly written. This is the correct question:

If sina×tan(a) = 1/2, find cosa

According to trigonometry identity;

tan a = sina/cosa

sina×tan(a) = sin a * sina/cosa

sin²a/cos a = 1/2

(1-cos²a)/cosa = 1/2

Cross multiply

2(1-cos²a) = cos a

2 - 2 cos²a = cos a

2cos²a + cos a - 2 = 0

Let P = cos a

2P² + P -2 = 0

P = -1 ±√1-4(2(2)/2(2)

P = -1 ±√1+16/4

P = -1 ±√17/4

P = -1±4.12/4

P = -1-4.12/4 and -1+4.12/4

P = -5.12/4 and 3.12/4

P = -1.28 and 0.78

Since P = cos a

Hence cos a = -1.28 and 0.78