Question

If cos x =-3/5 and pi /2 greater than x greater than pi, find the value of sin x /2

Answer 1

cos X = - 3

5

π < X < π

2

:. X lies in 2nd quadrant .

:. sin^2 x+ cos^2 X = 1

:. sin^2 X = 1 - cos^2 X

= 1 - ( - 3 )^2

( 5 )^2

= 1 - 9

25

= 25 - 9

25

:. sin^2 X = 16

25

taking sq. rt.

:. sin X = 4

5

4

:. sin X = 5

2 2

= 4 * 1

5 2

= 2

5