trig
posted by Ntombie .
Sketch the graph of f(x)=sin(x+30 degrees) and g(x)=cos2x in the same system of axis [180 degrees;180 degrees]

The graph of cos2x looks just like the graph of cos x, but oscillates twice as fast. So, since cos x crosses at 90 and 90, cos 2x crosses at 135, 45, 45, 135 deg.
The sin graph looks just like sin x, but is shifted to the left 30 deg. (That is, x+30 is zero when x=30. In effect, just draw a new yaxis at x=30 deg.)