Answers.com > Wiki Answers > Categories > Jobs & Education > Education > School Subjects > Math and Arithmetic > What is the law of cosines?

What is the law of cosines?

In: Math and Arithmetic [Edit categories]

Answer:

It is a mathematical equation that allows you to "solve" a triangle (find all length and angle values), if you know 2 sides and an included angle, or all three sides. It doesn't have to be a right triangle. You can find the cosine on a calculator easily.
c² = a² + b²- 2ab cos C
C = included angle
c = side opposite angle C (c)
a = side a
b = side b
The cosine law relates the length of the sides of a triangle to one of the angles in the triangle. If the triangle is labelled with vertices A, B, C with usual notation for edges (ie a is the side opposite the vertex A, so not touching A) and if x is the angle at vertex C then the cosine law says (c^2)=(a^2)+(b^2)-2abcos(x)

Note: There are comments associated with this question. See the discussion page to add to the conversation.

First answer by Quirkyquantummechanic. Last edit by Quirkyquantummechanic. Contributor trust: 3702 [recommend contributor ]. Question popularity: 15 [recommend question].

[report abuse]

Sources and related links: [Edit]

Wikipedia: Law of cosines

Can you answer these Math and Arithmetic questions?

	How do find the centimeter?	Answer it!
	How do you turn an improper fraction into an mixed number?	Answer it!
	What is the difference between the population mean and sample mean?	Answer it!
	How do you get the bonus in level 4 on run 2?	Answer it!
	What day is 2 years 7 months 4 days from today?	Answer it!

Relevant answers:

What are the formulas for law of sines and law of cosines?
sine: sin(A) sin(B) sin(C) cosines: a2=b2+c2-2bc cos(A) .........----- = ----- = ------ ........,,,.a .......b........ c a is side BC A is angle A sin(A) means sine of angle A psst, theres a law of...
Who discovered the law of cosines?
A caveman from 10,000 BC al-Kashi was the 1st to provide an explicit statement of the law of cosines in a form suitable for triangulation
When do you use the Law of Cosines?
We use the law of Cosines to be able to find : 1. The measure of the third side, when the measure of two sides and the included angle of a triangle ABC are known. 2. The measure of any angle, when...
Law of sines and cosines in mathematics?
Consider a triangle with vertices A, B and C. Call the edge opposite a given vertex by the same letter, but lower case. So side a is opposite vertex A etc. Law of Sines says: SinA/a= SinB/b=SinC/c If...
Law of cosines with a right angle?
The law of cosines with a right angle is just the pythagorean theorem. The cosine of 90 degrees is 0. That is why the hypotenuse squared is equal to the sum of both of the legs squared