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Answer:
y ≈ 10.6 cm
Explanation:
The cosine function relates the adjacent side to the hypotenuse in a right triangle. The side adjacent to the 20° angle is 10 cm.
cos(20°) = (10 cm)/y
y = (10 cm)/cos(20°)
y ≈ 10.6 cm
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Additional comment
The value of x is ...
x = (10 cm)tan(20°) ≈ 3.6 cm