Hi,
Can someone please help me with Question 4(ii) from the Specimen Paper A.
I understand, what process, that they're doing, trying to work out the area of triangle RQP in the middle by subtracting the smaller triangles, ARQ, BRP, QCP from the main triangle. I also understand how they start doing
AQ/C X AR/b. However, I don't understand how this process is then equal to cos2a.
Many thanks for any help!