WBJEE · Maths · Trigonometric Ratios & Identities
If \(\frac{\cos A}{3}=\frac{\cos B}{4}=\frac{1}{5},-\frac{\pi}{2} < A < 0,-\frac{\pi}{2} < B < 0\) then value of \(2 \sin A+4 \sin B\) is
- A 4
- B -2
- C -4
- D 0
Answer & Solution
Correct Answer
(C) -4
Step-by-step Solution
Detailed explanation
Hints : \(\cos A=\frac{3}{5} \quad \sin A=-\frac{4}{5}\) \[ \begin{aligned} & \cos B=\frac{4}{5} \quad \sin B=-\frac{3}{5} \\ & =2\left(-\frac{4}{5}\right)+4\left(-\frac{3}{5}\right)=-\frac{20}{5}=-4 \end{aligned} \]
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