Thursday, February 28, 2013

Math Mistakes: Law of Sines




Link to Math Mistakes

http://mathmistakes.org/?p=933 



What is wrong?
The mistake they did was when solving for the law of sines, they did not divide by the side corresponding to the angle. Instead, they only cross multiplied and did not divide to get sine B by itself. They left the decimal with sine of B instead of getting sine B on its own because that is what we are solving for. As a result, they got the wrong value for <B.

What they should have done:
When we are solving for the law of sines, we set up our magic number and our bridge. The angles must correspond to the sides. While this person set up the problem correctly, they solved it the wrong way. When you cross multiply you get 4.21sin30.4=1. 43sinB then, you divide by 1.43 to get sinB=1.49.  We should have taken the inverse sine but we notice that it is greater than one and it is not possible.
 

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