You can put this solution on YOUR website! What is the complementary angle of 13π/18
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There is no complementary angle of angles >= 90 degs (or >= pi/2 radians)
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13pi/18 radians is > pi/2
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If it's 13pi/18 degs, the complement = 90 - 13pi/18 degs
=~ 87.831 degs