Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Trigonometry

Question:

Find the value of cos15º sin7\(\frac{1}{2}\)º cos7\(\frac{1}{2}\)º

Options:

\(\frac{1}{2}\)

\(\frac{1}{4}\)

\(\frac{1}{8}\)

\(\frac{1}{16}\)

Correct Answer:

\(\frac{1}{8}\)

Explanation:

Multiply and divide the eq. by 2

⇒ cos15º sin7\(\frac{1}{2}\)º cos7\(\frac{1}{2}\)º

⇒ 2×\(\frac{1}{2×2}\)sin15º cos15º  (2sinA cos B = sin 2A ⇒ sin30º =\(\frac{1}{2}\))

⇒ \(\frac{sin30^o}{4}\)

= \(\frac{1}{8}\)