Further trigonometric identities

AHL 3.10

sin(A±B) cos(A±B)=sinAcosB±cosAsinB📖 =cosAcosB∓sinAsinB📖

AHL 3.9

If we take the identity sin2θ+cos2θ=1 and divide through by cos2θ we find

1+tan2θ=sec2θ📖

AHL 3.9

If we take the identity sin2θ+cos2θ=1 and divide through by sin2θ we find

1+cot2θ=cosec2θ📖

AHL 3.10

The double angle identity for tan states that

tan2θ=1−tan2θ2tanθ📖

AHL 3.10

The compound angle identity for tan states that

tan(A±B)=1∓tanAtanBtanA±tanB📖

Exercises