Originally Posted by

**ImanAA** Can someone please explain to me, step by step how to arrive at the final answer. Im finding questions containing the theta sign rather than actual values for theta confusing.

I also dont know how to draw the theta sign on here so Ive just used x for ease.

The question is - Express the following as a single sine, cosine or tangent:

cos4x cos3x - sin4x sin3x

The solution I have breaks the answer down to cos(4x + 3x) which results in cos7x but I dont understand why this is also not the case for sine4x sin3x