Question

Use an Addition or Subtraction Formula to find the exact value of the expression.

a)tan 255°

 

Answer 1

tan 255   =   tan(180 + 75)

               =   tan(75)

               =   tan(45 + 30)

               =   [ tan(45) + tan (30) ] / [ 1 - tan (45) tan (30) ]

               =   [ (sqrt(3) + 1)/sqrt(3)) ] / [ (sqrt(3) - 1)/sqrt(3)]

tan 255    =   [ sqrt(3) + 1] / [ sqrt(3) - 1 ]