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The cosine function in the unit circle

The unit circle is assigned with the angle alpha in the center of the x-coordinate from the intersection S on the circle as the cosine. This means that in the unit circle, the adjacent of alpha is equal to the cosine of alpha.

Cognitions that are recognized on the base of the unit circle

cos (90° - x) = - cos (90° + x)

cos (180° - x) = cos (180° + x)

cos a = - cos (a+180)

Cos 45° = sin 45° =  àexplanation for that: The sine and cosine make a right angled triangle with the radius 1 (= hypotenuse). The theorem of Pythagoras is used: a² + b² = c² oder ½ + ½ = 1. The root of ½ is consequently one of the sides, and then the nominator is made rational:.

Cosine function in the coordinate system

The cosine curve is an odd function that is symmetric to the y-axis and that repeats itself after 360 degrees (Periodically).

Besondere Werte, die in der Kosinusfunktion beim Einheitskreis und im Koordinatensystem gelten

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02/09/07