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Mathematics

Assertion (A): If 4 cos θ = 11 sin θ, the value of 11cosθ7sinθ11cosθ+7sinθ=93149\dfrac{11\text{cosθ} - 7 \text{sinθ}}{11 \text{cosθ} + 7 \text{sinθ}}=\dfrac{93}{149}.

Reason (R): tan θ = sin θcos θ\dfrac{\text{sin θ}}{\text{cos θ}}

  1. A is true, R is false.
  2. A is false, R is true.
  3. Both A and R are true.
  4. Both A and R are false.

Trigonometric Identities

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Answer

Both A and R are true.

Explanation

Given,

4 cos θ = 11 sin θ

⇒ sin θ = 411\dfrac{4}{11} cos θ

sinθcosθ=411\dfrac{sin θ}{cos θ} = \dfrac{4}{11}

Let sin θ = 4a and cos θ = 11a.

11cosθ7sinθ11cosθ+7sinθ=11×11a7×4a11×11a+7×4a=121a28a121a+28a=93a149a=93149\dfrac{11\text{cosθ} - 7 \text{sinθ}}{11 \text{cosθ} + 7 \text{sinθ}}\\[1em] = \dfrac{11 \times 11a - 7 \times 4a}{11 \times 11a + 7 \times 4a}\\[1em] = \dfrac{121a - 28a}{121a + 28a}\\[1em] = \dfrac{93a}{149a}\\[1em] = \dfrac{93}{149}

∴ Assertion (A) is true.

sin θ = PerpendicularHypotenuse\dfrac{Perpendicular}{Hypotenuse}

cos θ = BaseHypotenuse\dfrac{Base}{Hypotenuse}

tan θ = PerpendicularBase\dfrac{Perpendicular}{Base}

= PerpendicularHypotenuseBaseHypotenuse\dfrac{\dfrac{Perpendicular}{Hypotenuse}}{\dfrac{Base}{Hypotenuse}}

= sin θcos θ\dfrac{\text{sin θ}}{\text{cos θ}}

∴ Reason (R) is true.

Hence, both Assertion (A) and Reason (R) are true.

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