SOLUTION: tan (-5pi/12) Use an Addition or Subtraction Formula to find the exact value of the expression

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Question 871054: tan (-5pi/12)
Use an Addition or Subtraction Formula to find the exact value of the expression

Answer by lwsshak3(11628)   (Show Source): You can put this solution on YOUR website!
tan (-5pi/12)
Use an Addition or Subtraction Formula to find the exact value of the expression.
***
tan(-5π/12)=tan(4π/12-9π/12)=tan(π/3-3π/4)
Identity: tan(s-t)=(tan s-tan t)/(1+tan s*tan t
tan(π/3-3π/4)=tan(π/3-tan(3π/4))/(1+tan(π/3*tan(3π/4)
=(√3+1))/(1+(√3*-1)
=(√3+1))/(1-√3)
=(√3+1))/(1-√3)
Calculator check:
tan(-5π/12)≈-3.732…
Exact value=(√3+1))/(1-√3)≈-3.732…

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