Posted by **robert** on Monday, August 3, 2009 at 9:22pm.

need an aswer quich ok thiers two the find sin(2pi/3 -pi/4) using sum and difference identites and then tan 5pi/12 using the same identites

- math -
**bobpursley**, Monday, August 3, 2009 at 9:28pm
You have a formula for

Sin(A-B)

Use that on the first one.

Now on the second, recall that

5PI/12= 3PI/12 + 2PI/12=PI/4 +PI/6

You now can use the tan (A+B) formula, as you know the tan(PI/4) and tan(PI/6)

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