Question

5. Which is equivalent to 1/2

? Select all that apply.
A sin 30°
B sin 45°
C cos 45°
D cos 60°
E tan 30°
F tan 45º

Answer 1

• A sin 30°
• D cos 60°

Explanation:

Attached is a short table of trig function values. There are really only three you need to remember if you keep an image of the sine and cosine graphs in your head (for 0° and 90° values).

sin(α) = cos(90°-α)

tan(α) = sin(α)/cos(α)

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sin(30°) = cos(60°) = 1/2 . . . . . . . the answer to this question

sin(45°) = cos(45°) = 1/√2 = (√2)/2

sin(60°) = cos(30°) = (√3)/2

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I find it just as easy to remember SOH CAH TOA and the side ratios in isosceles and half-equilateral right triangles: 1:1:√2 and 1:√3:2, respectively.