C2 TRIG

Question 20 in the mixed exercise of trig identities...


This is the link to the question if you need the full thing...

https://doc-14-5o-docs.googleusercontent.com/docs/securesc/4146934clisd301f8nhbhh8ifq6krti3/1j0q5r15b0t4if93ad8rcsbc8g4soj5d/1459684800000/01042298237316186224/01600185217438677532/0B1ZiqBksUHNYeTh1MnhZTHM4VTg

Question 20 in the mixed exercise of trig identities...

The diagram shows part of a curve with equation f(x) = 1+2sin(px+q) p and q being positive constants and q < 90.

Give than the coordinates of A and C are (0,2) and (45,0) respectively:

Calculate value of q - DONE

show that p = 4

Not sure how to do this one.. I get so far as...

sin(45p +30) = -30

But when I looked up the answer it should be

sin (45p+30) = 210

I now p is supposed to be postive - but just not sure where the 210 comes from because i get -30.....

Thanks for any help you can give :-)

This is the link to the question if you need the full thing...

https://doc-14-5o-docs.googleusercontent.com/docs/securesc/4146934clisd301f8nhbhh8ifq6krti3/1j0q5r15b0t4if93ad8rcsbc8g4soj5d/1459684800000/01042298237316186224/01600185217438677532/0B1ZiqBksUHNYeTh1MnhZTHM4VTg

The link does not work
Better fix it !!

Remember sin has two solutions (by this I mean the other solutions are just +/- 360 degrees). Say one is x. The other one is then 180-x. In your case 180--30=210 (degrees)