Sketch the curves y=sin(x) and y=cos(x) over the interval (0, 2 pi).

You will observe that there are two points at which the cross, and the

x's for these points are the values for which sin(x)=cos(x) and so are

the values of a that you require.

sin(a)=cos(a)

can be rearranged to tan(a)=1, so one solution is 45 degrees (pi/4 radian)

The other solution is in the third quadrant (where tan is positive) and so

is 180+45 degrees (pi+pi/4 radian)

RonL