sin (a + B) Derive the identity for tan (o + B) using tan (a + B) = . After applying the formulas for sums of sines and cos (a + B) cosines, divide the numerator and denominator by cos a cos B. Apply the formulas for sums of sines and cosines. sin (a + B) tan (a + B) = cos (a + B) Divide the numerator and denominator by cos a cos B. cos a cos B tan (o + B) = cos a cos B Divide each term in the numerator and denominator by cos a cos B. Divide each term in the numerator and denominator by cos a cos B. sin a - cos a . cos a cos B cos a cos B tan (a + B) = cos a . sin a . cos a cos B cos a cos B 0.1+1 .0 1 .1 - . tan B Simplify