AP EAMCET · Maths · Trigonometric Ratios & Identities
\[
\sin 21^{\circ} \cos 9^{\circ}-\cos 84^{\circ} \cos 6^{\circ}=
\]
- A 1
- B \(\frac{1}{4}\)
- C \(\frac{1}{2}\)
- D \(\frac{3}{2}\)
Answer & Solution
Correct Answer
(B) \(\frac{1}{4}\)
Step-by-step Solution
Detailed explanation
\(\begin{aligned} & \text { } \sin 21^{\circ} \cos 9^{\circ}-\cos 84^{\circ} \cos 6^{\circ} \\ & =\frac{1}{2}\left[2 \sin 21^{\circ} \cos 9^{\circ}-2 \cos \left(90^{\circ}-6^{\circ}\right) \cdot \cos 6^{\circ}\right]\end{aligned}\)…
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