SOLUTION: How do I go about finding the exact value of tan(pi/4-pi/3)?

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Question 69609: How do I go about finding the exact value of tan(pi/4-pi/3)?
Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!

How do I go about finding the exact value
of tan%28pi%2F4-pi%2F3%29?

You have to know the formula 

tan%28A-B%29=%28tan%28A%29-tan%28B%29%29%2F%281%2Btan%28A%29tan%28B%29%29

Substitute pi%2F4 for A and pi%2F3 for B:



Now you have to know that

tan%28pi%2F4%29+=+1 and that tan%28pi%2F3%29=+sqrt%283%29

So substitute these:

tan%28pi%2F4-pi%2F3%29=%281-sqrt%283%29%29%2F%281%2B%281%29sqrt%283%29%29

or

tan%28pi%2F4-pi%2F3%29=%281-sqrt%283%29%29%2F%281%2Bsqrt%283%29%29

Your teacher may accept it that way, but s/he 
probably would prefer that you rationalize the 
denominator:





tan%28pi%2F4-pi%2F3%29=%281-2sqrt%283%29%2B3%29%2F%281-3%29

tan%28pi%2F4-pi%2F3%29=%284-2sqrt%283%29%29%2F%28-2%29

Factor 2 out of the numerator

tan%28pi%2F4-pi%2F3%29=%282%29%282-sqrt%283%29%29%2F%28-2%29

Cancel the -2 in the bottom into the
2 in the top, getting -1 in the top:

tan%28pi%2F4-pi%2F3%29=+-1%282-sqrt%283%29%29
 
Remove the parentheses:

tan%28pi%2F4-pi%2F3%29=+-2%2Bsqrt%283%29

or you can save one sign by writing the
second term first

tan%28pi%2F4-pi%2F3%29=+sqrt%283%29-2

Edwin