Based on the following information from a past paper:
Since p = sin40 and q = cos110.
and therefore sin140 = p and cos70 = - q
One of the questions was:find an expression for cos140
In the mark scheme the answer was:
cos^2(X) + sin^2(X) = 1 (I understand the importance of using the trig identity)
followed by: cos(140) = √(1 - sin^2(X)) (I got this far)
this is the bit which I do not understand which was in the mark scheme:
cos(140) = √(1 - p^2)
How does p = sin x ?
all the information that it gives is that p = sin40, so how can that be applied in general?