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Angles α and β are the two acute angles in a right triangle. Use the relationship between sine and cosine to find the value of β if β > α.

sin (x/2+20) = cos (2x-25/2)

A) 25°

B) 33°

C) 36.5°

D) 53.5°

HINT: Sine and cosine of complementary angles are related

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Answers (1)
  1. 3 May, 07:34
    0
    D) 53.5°

    Step-by-step explanation:

    Sine and cosine of complementary angles are equal:

    sin θ = cos (90 - θ)

    sin (x/2 + 20) = cos (2x - 25/2)

    cos (90 - (x/2 + 20)) = cos (2x - 25/2)

    90 - (x/2 + 20) = 2x - 25/2

    90 - x/2 - 20 = 2x - 25/2

    165/2 = 5x/2

    5x = 165

    x = 33

    x/2 + 20 = 36.5

    2x - 25/2 = 53.5

    Since β > α, β = 53.5°.
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