Question

if sin a = -3/5 and lies in 3 quadrant then the value of cos(a/2) is?

Answer 1

@triciaal

Answer 2

@ganeshie8

Answer 3

ok then?

Answer 4

Since "a" is in the third quadrant, cosine will also be negative and it is -4/5 from the above diagram. Using the half angle formula: cos(a) = 2cos^2(a/2) - 1.
-4/5 = 2cos^2(a/2) - 1
1 - 4/5 = 2cos^2(a/2)
2cos^2(a/2) = 1/5
cos^2(a/2) = 1/10
cos(a/2) = plus or minus square root of 1/10
Since a is in the third quadrant, a/2 will be in the second quadrant where cosine is negative. Therefore, \(\cos(a/2) = -\frac{1}{\sqrt{10}} \)

Answer 5

okey thanku