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Maths Exercices
Trigonometric functions at related angles

Using the geometric symmetry of the unit circle, some trigonometric functions can be established. You can calculate the trigonometric functions of an angle in the second, third or fourth quadrant using its ratio with the first quadrant.

Complementary angles.
Two angles are complementary if they add up to 90 degrees.

Ángulo  complementarioIf A and B are two angles where A+B=90º, that is, B=90º - A, we have:
sinA = cos B, so that, sin A = cos(90º-A)
cosA = sin B , so that, cosA=sin(90º-A)
Similarly, tanA = cotB


If sinA = 0.866 and cosA = 0.5

Calculate the sine, cosine and tangent of the complementary angle of A.

Solution: Sine = Cosine = Tangent =
(round the solution to thousandths)