This topic is part of the HSC Mathematics Extension 1 syllabus under the topic Trigonometric Functions.

In this post, we will explore further trigonometric techniques on how to solve trigonometric equations requiring factorising and/or the application of compound angle and double angle formulae. The formulae for these are the following:

sin(A+B) = sin(A)cos(B) + sin(B)cos(A) sin(A-B) = sin(A)cos(B) - sin(B)cos(A) cos(A+B) = cos(A)cos(B) - sin(A)sin(B) cos(A-B) = cos(A)cos(B) + sin(A)sin(B)These further trigonometric techniques can be found in the following video.

### Sum & difference trigonometric identities

### Proving the compound angle identities geometrically

### Proving the compound angles graphically

### Cos and Tan results