Hi, can someone please show me the solution to this? I have no idea where to start. I've never had this concept explained to me. I tried asking a previous question before, but the answers were too complex (except for the one where I just had to sub in..)
Is their a introductory site where I can learn trig identities and stuff like these?
Hint
For a right triangle, Pythagoras theorem is $$AC^2+BC^2=AB^2$$ You know $AB$ and $BC$; so $AC=???$
For the trigonometric questions, I suppose that you remember that $\cos B=\frac{BC}{AB}$
Just continue along this way. They basically ask you if you remember some definitions.