Practicing Success
The value of $\frac{\left(\cos 9^{\circ}+\sin 81^{\circ}\right)\left(\sec 9^{\circ}+{cosec} 81^{\circ}\right)}{2 \sin ^2 63^{\circ}+1+2 \sin ^2 27^{\circ}}$ is: |
$\frac{1}{2}$ $\frac{4}{3}$ 2 1 |
$\frac{4}{3}$ |
By using concept :- sinA = ccosB Iff A + B = 90º sinA = \(\frac{1}{cosecA}\) secA = \(\frac{1}{cosA}\) sin²A + cos²A = 1 Now, \(\frac{(cos9º+sin81º).(sec9º+cosec81º)}{2sin²63º + 1 + 2 sin²27º}\) = \(\frac{ cos9º.sec9º + cos9º.cosec81º + sin81º.sec9º+ sin81º.cosec81º}{2sin²63º + 1 + 2 cos²63º}\) = \(\frac{ 1 + sin81º.cosec81º + cos9º.sec9º+1}{2 + 1 }\) = \(\frac{ 1 + 1 +1+1}{2 + 1 }\) = \(\frac{4}{3 }\) |