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October 9, 2015
Posted by **-** on Sunday, November 8, 2009 at 2:46pm.

can be written as

tan(x+y) = (tanx + tany) / (1 - tanxtany)

- advanced functions -
**bobpursley**, Sunday, November 8, 2009 at 3:03pmrewrite the left side as

sin(x+y)/cos(x+y), then use the addition formulas for both. It will simplify (finally) to the right.