What relationship do the ratios of sin x and cos y share ?

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The sine of the measure of an angle in a right triangle, is the ratio of the opposite side of that angle, to the hypotenuse.

The cosine of the measure of an angle in a right triangle, is the ratio of the adjacent side of that angle, to the hypotenuse.

According to these, we have:



and

.

Thus, the ratios of both are identical 

Exponential function