Question 568922
Find the exact values of sin13/6π, cos13/6π, and tan13/6π. 
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(13/6π)=(13π/6)=(12π/6+π/6)=(2π+π/6)

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sin(13π/6)=sin(2π+π/6)=sin(π/6)=1/2
cos(13π/6)=sin(2π+π/6)=cos(π/6)=√3/2
tan(13π/6)=tan(2π+π/6)=tan(π/6)=√3/3
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you could have use the trig addition formulas for sin, cos and tan, and you would get the same answers.