Basic Trigonometry Facts

Algebra: Trigonometry Help


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360 degrees = 2p radians
so, 180 degrees = p radians

eq001eq002Eq003

Eq004Eq005

The original angle can be found by using the inverse trig function. For example:

Eq006
Sometimes in the literature, arcsin is written as sin-1 and so on to indicate that it is an inverse function.

In the following examples, the side lengths are found using the Pythagorean theorem.

sin 45o = cos 45o = 1/1.4142 = 0.7071
tan 45o = cot 45o = 1/1 = 1

sin 30o = cos 60o = 1/2 = 0.5
cos 30o = sin 60o = 1.7321/2 = 0.8661
tan 30o = cot 60o = 1/1.7321 = 0.5774
cot 30o = tan 60o = 1.7321/1 = 1.7321

Then, there are the special cases of 0 and 90o.

Angle sin cos tan
0 0 1 0
90 1 0 Infinity

The sin and cos for the full circle (0 to 360o) are spelled out in the quadrant trigonometry facts help page.