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MHT CET · Maths · Trigonometric Ratios & Identities

\(\sin 690^{\circ} \times \sec 240^{\circ}=\)

  1. A \(1\)
  2. B \(-1\)
  3. C \(\frac{-1}{2}\)
  4. D \(\frac{1}{2}\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(1\)

Step-by-step Solution

Detailed explanation

\(\sin 690^{\circ} \times \sec 240^{\circ}\)
\(=\sin \left(1 \times 360^{\circ}+330^{\circ}\right) \times \sec \left(180^{\circ}+60^{\circ}\right)\)
\(=\sin 330^{\circ} \times\left(-\sec 60^{\circ}\right)\)
\(=\sin \left(2 \pi-30^{\circ}\right) \times(-2)\)
\(=-2\left(-\sin 30^{\circ}\right)=(-2)\left(-\frac{1}{2}\right)=1\)