Thread: trignometric equations help

(b) The diagram shows part of the curve with equation y=cos(px−q)° , where p and q are positive constants and q<180. The curve cuts the x-axis at points A, B and C, as shown.
Given that the coordinates of A and B are (100, 0) and (220, 0) respectively:
(i) Write down the coordinates of C.
(ii) Find the value of p and the value of q.

I have guessed that the coordinates of C is (340,0), which is correct, but is there any 'formal' way of working out the coordinates of C?

Also can someone show me how to work out the vales of p and q?

thank you.

Hi



A, B and C are consecutive zeros of cos(px-q) therefore







Subtracting gives



Then or

And