Here’s a sample SPM Question that requires you to use Double Angle and Half Angle Formulae.

Given that sin x = 5/13, and that x is obtuse. Calculate without using a calculator the value of

a) tan 2x

b) cos (x/2)

The technique used here is the same as for the Addition Formulae which I explained in **this video.**

Answers

a) -120/119

b) Square root of (1/26)

Here’s the Video Tutorial if you’re stuck.

Part 1 (Question a)

Part 2 (Question b)

PS : – If you’ve enjoyed this tutorial, please share it with your friends. Just click below on the “Share on Facebook” link below.

## Trackbacks/Pingbacks