Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Trigonometry

Question:

If cos4x - sin4x = \(\frac{3}{5}\), find 1 - 2sin2x + 2 sinx cosx is equal to:

Options:

\(\frac{3}{4}\)

\(\frac{7}{5}\)

\(\frac{5}{7}\)

0

Correct Answer:

\(\frac{7}{5}\)

Explanation:

⇒ cos4x - sin4x = \(\frac{3}{5}\)

⇒ (cos2x + sin2x) (cos2x - sin2x) = \(\frac{3}{5}\)

⇒ (cos2x - sin2x) = \(\frac{3}{5}\)

⇒ (cos 2A) = \(\frac{3}{5}\)

So,

⇒ (1 - 2sin2x) + (2 sinx cosx)

= (cos2x) + (sin2x)

= \(\frac{3}{5}\) + \(\frac{4}{5}\)

= \(\frac{7}{5}\)