Question

The Law of Cosines states that a^2 = b^2 - c^2 + 2bc cos A.

-Is this true or false? I can't find the answer anywhere in my book.

Answer 1

google law of cosines

Answer 2

False I believe it should look like

a² = b² + c² - 2bc cosA

Answer 3

the 2bc should be negative but besides that it is correct

Answer 4

so i guess technically it is false

Answer 5

it false. Thanks for the help guys!

Answer 6

no problem!

Answer 7

\[\cos A=\frac{ b ^{2}+c ^{2}-a ^{2} }{2bc }\]
\[2bc \cos A=b ^{2}+c ^{2}-a ^{2}\]
now you can solve