Sender: pierre boivin
Subject: sines & cosine law

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.

Hi Pierre,

If a triangle has two sides of length 7.2 and 5.9 and the angle between these sides is 71o 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.


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