Question

Given cos alpha=15/17 in Q1, find cos(alpha/2) And sin(alpha/2)​

Answer 1

• cos(α/2) = (4/17)√17

• sin(α/2) = (√17)/17

Explanation:

The appropriate hαlf-angle identities are:

sin(α/2) = √((1 -cos(α))/2)

cos(α/2) = √((1 +cos(α))/2)

Putting in your given values for cos(α), we have ...

cos(α/2) = √((1 +15/17)/2) = √(16/17) = 4(√17)/17

sin(α/2) = √((1 -15/17)/2) = √(1/17) = (√17)/17