CALCULUS Understanding Its Concepts and Methods

Law of cosines and law of sines

Let , , and be the sides of a triangle.

Law of cosines. If
is the angle between
and
,
then

If
,
then
and we get the Pythagorean
theorem.

Law of sines. If
,
,
and
are the angles opposite the sides
,
,
and
,
then

If
,
then
and we get
;
that is, the sine of an angle is equal to the opposite side over the
hypotenuse.

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Copyright © 2006 Darel Hardy, Fred Richman, Carol Walker, Robert Wisner. All rights reserved. Except upon the express prior permission in writing, from the authors, no part of this work may be reproduced, transcribed, stored electronically, or transmitted in any form by any method.