Question
If $\sin2\text{A}=\lambda\sin2\text{B},$ then write the value of $\frac{\lambda+1}{\lambda-1}.$

Answer

We have,
$\sin2\text{A}=\lambda\sin2\text{B}$
$\Rightarrow\ \frac{\sin2\text{A}}{\sin2\text{B}}=\lambda$
$\Rightarrow\ \frac{\sin2\text{A}}{\sin2\text{B}}+1=\lambda+1$
$\Rightarrow\ \frac{\sin2\text{A}+\sin2\text{B}}{\sin2\text{B}}=\lambda+1...(\text{i})$
Again,
$\sin2\text{A}=\lambda\sin2\text{B}$
$\Rightarrow\ \frac{\sin2\text{A}}{\sin2\text{B}}=\lambda$
$\Rightarrow\ \frac{\sin2\text{A}}{\sin2\text{B}}-1=\lambda-1$
$\Rightarrow\ \frac{\sin2\text{A}-\sin2\text{B}}{\sin2\text{B}}=\lambda-1...(\text{ii})$
Dividing equation (i) by equation (ii), we get
$\frac{\sin2\text{A}+\sin2\text{B}}{\sin2\text{A}-\sin2\text{B}}=\frac{\lambda+1}{\lambda-1}$
$\Rightarrow\ \frac{2\sin\Big(\frac{2\text{A}+2\text{B}}{2}\Big)\cos\Big(\frac{2\text{A}-2\text{B}}{2}\Big)}{2\sin\Big(\frac{2\text{A}-2\text{B}}{2}\Big)\cos\Big(\frac{2\text{A}+2\text{B}}{2}\Big)}=\frac{\lambda+1}{\lambda-1}$
$\Rightarrow\ \frac{\sin(\text{A+B})\cos(\text{A}-\text{B})}{\sin(\text{A}-\text{B})\cos(\text{A}+\text{B})}=\frac{\lambda+1}{\lambda-1}$
$\Rightarrow\ \frac{\sin(\text{A+B})\cos(\text{A}-\text{B})}{\cos(\text{A+B})\sin(\text{A}-\text{B})}=\frac{\lambda+1}{\lambda-1}$
$\Rightarrow\ \frac{\tan(\text{A+B})}{\tan(\text{A}-\text{B})}=\frac{\lambda+1}{\lambda-1}$
$\therefore\ \frac{\lambda+1}{\lambda-1}=\frac{\tan(\text{A+B})}{\tan(\text{A}-\text{B})}.$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free