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AP EAMCET · Maths · Trigonometric Ratios & Identities

If \(\cos ^3 \mathrm{x} \sin 4 \mathrm{x}=\sum_{\mathrm{r}=0}^{\mathrm{n}} \mathrm{a}_{\mathrm{r}} \sin \mathrm{rx} \forall \mathrm{x} \in \mathbb{R}\), then \(a_3+a_5: a_1+a_7=\)

  1. A \(1: 3\)
  2. B \(1: 1\)
  3. C \(2: 1\)
  4. D \(3: 1\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(3: 1\)

Step-by-step Solution

Detailed explanation

\(\cos ^3 x \cdot \sin 4 x=\frac{1}{2}(2 \sin 4 x \cdot \cos x) \cos ^2 x\)…