Review question

# Can we solve $\tan\theta\tan(\theta+\pi/3)=2$? Add to your resource collection Remove from your resource collection Add notes to this resource View your notes for this resource

Ref: R6039

## Suggestion

Prove that, if $\tan\theta\tan(\theta+\alpha)=k$, then $(k+1)\cos(2\theta+\alpha)=(1-k)\cos\alpha.$

Solve the equation $\tan\theta\tan(\theta+\pi/3)=2.$

Discuss the equation $\tan\theta\tan(\theta+\alpha)+1=0.$

Can you think of any formulae relating $\sin, \tan$ and $\cos$?

Can we expand $\cos A\cos B$? Or $\sin A \sin B$?

If we can’t do the first part, can we still do the second and third parts (using the result from the first part)?