The value of  cosec 20° - sec 20° is equal to?

This question was previously asked in
NDA (Held On: 10 Sept 2017) Maths Previous Year paper
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  1. 4
  2. 2
  3. 1
  4. -4

Answer (Detailed Solution Below)

Option 1 : 4
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NDA 01/2025: English Subject Test
30 Qs. 120 Marks 30 Mins

Detailed Solution

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CONCEPT:

Trigonometric Identities:

  • (cos A× cos B) – (sin A × sin B) = cos(A + B)
  • 2 × sin A × cos A = sin (2A)
  • sin (90 - θ) = cos θ

 

CALCULATION:

Given that: √3 cosec 20° – sec 20°

As we know that, cosec θ = 1/ sin θ and sec θ = 1/ cos θ

As we know that, cos 30° = √3 / 2, sin 30° = ½

As we know that, (cos A × cos B) – (sin A × sin B) = cos(A + B)

As we know that, 2 × sin A × cos A = sin (2A)

As we know that, sin (90 - θ) = cos θ

⇒ 4

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