1. triangles

just a few questions: what is the cosine rule? and the sine rule? any formulas? thanks!

2. Originally Posted by miley_22
just a few questions: what is the cosine rule? and the sine rule? any formulas? thanks!
Given a triangle with sides a, b, and c, and angles opposite those sides A, B, and C respectively:
This is the Law of Sines:
$\frac{a}{sin(A)} = \frac{b}{sin(B)} = \frac{c}{sin(C)}$

These are the Law of Cosines:
$a^2 = b^2 + c^2 - 2bc~cos(A)$

$b^2 = a^2 + c^2 - 2ac~cos(B)$

$c^2 = a^2 + b^2 - 2ab~cos(C)$
(The Law of Cosines may be thought of as a generalization of the Pythagorean Theorem to triangles not necessarily including a right angle.)

-Dan