Question

Which angle is equal to half of its complement.

Answer 1

This problem is checking to see if you know what complementary angles are. Complementary angles are two angles that add up to a right angle (90 degrees). By the way, you don't need it for this problem, but another useful definition is supplementary angles: two angles that add up to 180 degrees. ...
Let a = an acute angle (an acute angle is < 90 degrees)
Let b = its complement (another acute angle)
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We know by their definition that:
a + b = 90
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We are given a is half as large as its complement, b:
b = 2a
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Use substitution and insert the identity for b into the first equation:
a + b = 90
a + 2a = 90
3a = 90
a=30