# Trigonometry Tricks

## cos(90° - x) = sin x

## sin(90° - x) = cos x

__Examples:__

cos 75° = .259...

cos 15° = .259...

cos 45° = .707...

sin 45° = .707...

**(Notice that the sine & cosine of 45 degrees are exactly the same!)**

*I almost forgot that most of the time, sines, cosines, tangents and such are irrational numbers; this explains the triple periods after the numbers in the examples.*

## Something to remember about real numbers:

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© Derek Cumberbatch