Monday, May 21, 2007
posted by Jennifer at 8:13 PM
The cosine law formula
a2 = b 2 + c2 - 2bc cos A







Write down the formula
a 2 = b 2 + c 2 - 2bcCos A

Fill in the blanks
a 2 = 9.0 2 + 7.8 2 - 2(9.0)(7.8)cos 112

Finally answer the question
a 2 = 60.84 + 81 - -52.6

a 2 = 194.44

square root
a 2

square root
194.44
a = 13.9

Congratulations

you just learned how to find a side using Cosine Law
Now learn how to find an angle with cosine law


Change around the question switch the spots of a & c so that you are looking for c /cosC
c 2 = a 2 + b 2 -2abCos C

17.2 2 = 24.2 2 + 19.5 2 - 2(24.2)(19.5)cos C




Congratulations again
you finished your cosine law lesson :)