Question 86725
need to get rid of either the sin or cos... to make an equation in just one "variable". The obvious one is the sin 2x since there is a formula:
sin2x = 2sinx cosx

so, 2sinXcosX - cosX = 0

looking at this, we have a cosX in both terms so we can factorise.... solving any equation we are always looking to factorise:

cosX(2sinX-1) = 0

which means that either
cosX=0 or 2sinX-1 = 0
cosX=0 or 2sinX = 1
cosX=0 or sinX = 1/2
X=90 or X=30... in the first quadrant. There are other angles that give these answers too but you do not quote the range of angles acceptable.


hope this helps
Jon