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Question

If x, y are acute angles, where 0 < x + y < 90° and sin(3x - 40°) = cos (3y + 40°), then the value of tan (x + y) is equal to

The correct answer is \(\frac{1}{\sqrt{3}}\)

Given:

sin(3x - 40°) = cos (3y + 40°)

Used Formula:

sinA = cosB

Then, A + B = 90°

Calculation:

sin(3x - 40°) = cos (3y + 40°)

⇒ 3x – 40° + 3y + 40° = 90°

⇒ 3x + 3y = 90°

⇒ x + y = 30°

Therefore, tan(x + y) = tan30° = 1/√3

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Important Questions from Trigonometric Ratios and Identities

  1. What is the ratio of the greatest to the smallest value of 2 – 2 sin x – sin 2x, 0 ≤ x ≤ (π/2)? 

  2. If sinθ = \(\frac{4}{5}\) , Find the value of sin3θ

  3. What is (1 + cot θ - cosec θ)(1 + tan θ + sec θ) equal to?

  4. If \(\sin \theta =\frac{3}{5}\)  and  \(\cos \theta =\frac{4}{5}\) , then the value of  \(\frac{1+\tan \theta}{1-\cot \theta}\)  is:

  5. If cos x = p/q and 0° < x < 90°, then the value of tan x is:

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