Triangle LMN, angle L=71 degree , LM= 7.2 , MN=8.3 , ln= 5.9

The questiion was to find angle M. Using the cosine law I found the answer to be 44 degree. It is also the book answer. Using the sines law I found the answer to be 42.2 degree. why can't I use the sines law.

Thank you.
Pierre

Hi Pierre,

If a triangle has two sides of length 7.2 and 5.9 and the angle between these sides is 71^o then using the the law of sines the third side is of length 8.53346 not 8.3. Either that or L is not 71 degrees. Something is inconsistent here because a triangle is determined by three of the four items you listed.

Cheers,
Chris