Multiple Angles - SS3 Mathematics Lesson Note Change Class & Subject Change Topic & Year sin2A=2sinAcosA cos2A=1−2sin2A or cos2A=2cos2A−1 tan2A= 2tanA1−tan2A sin3A= 3sinA−4sin3A cos3A=4cos3A−3cosA tan3A= 3tanA−tan3A1−3tan3A sin2A=12(1−cos2A) cos2A=12(1+cos2A) Example 4 Evaluate tan2θ, if tanθ=43 Solution tan2θ= 2tanθ1−tan2θ =2(43)1−(43)2= 831−169=83−79=83×−97=−247