Trigonometry identities
From Conservapedia
Contents
Pythagorean identities
Law of sines
The law of sines for an arbitrary triangle states:
or equivalently:
Law of cosines
The law of cosines (also known as the cosine formula) is an extension of the Pythagorean theorem to arbitrary triangles:
or equivalently:
Sum and difference identities
Double-angle identities
Half-angle identities
Note that 
are correct, it means it may be either one, depending on the value of A/2.
Law of tangents
The law of tangents:
