6th December 2019

17

What is the formula of cosine?

The cosine rule. We can use the cosine formula to find the length of a side or size of an angle. For a triangle with sides a,b and c and angles A, B and C the cosine rule can be written as: a2 = b2 + c2 - 2bc cos A.

Correspondingly, what is the law of cosines?

The Law of Cosines is useful for finding: the third side of a triangle when we know two sides and the angle between them (like the example above) the angles of a triangle when we know all three sides (as in the following example)

What is the equation for the law of cosines?

The cosine of a right angle is 0, so the law of cosines, c2 = a2 + b2 – 2ab cos C, simplifies to becomes the Pythagorean identity, c2 = a2 + b2, for right triangles which we know is valid. Case 3. In this case we assume that the angle C is an acute triangle.
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