Hello mike--1988 Originally Posted by
mike--1988 hi ,im struggling with this question,all help greatly appreciated
this is the proof question ..
sin(A+B) / sin(A-B) = (tanA + tanB) / (tanA - tanB )
$\displaystyle \frac{\sin(A+B)}{\sin(A-B)}=\frac{\sin A \cos B + \cos A \sin B}{\sin A \cos B - \cos A \sin B}$
Divide top and bottom by $\displaystyle \cos A \cos B$:$\displaystyle =\frac{\dfrac{\sin A}{ \cos A} + \dfrac{\sin B}{\cos B}}{\dfrac{\sin A}{ \cos A} - \dfrac{\sin B}{\cos B}}$
$\displaystyle =\frac{\tan A + \tan B}{\tan A - \tan B}$
Grandad