10-2

Formulas:

• tan (A+B) = ( tanA + tanB )/( 1 -tanAtanB )


• tan (A-B) = ( tanA -tanB )/( 1 + tanAtanB )

Ex1: If tan A = 1/4 and tan B = 1/5

a. Find tan (A+B)

(tan A + tan B )/( 1 –tan A*tan B ) is the formula. Now you need to REPLACE tan A and tan B for the values they gave you. YOU HAVE TO USE THE FORMULAS.

( 1/4 + 1/5 )/(1 -(1/4)(1/5)) You don't need a calculator to do this.

( 5/20 + 4/20 )/( (20/20) -(1/20))

(9/20)/(19/20)

180/380

9/19

b. Find tan (A-B)

the formula is ( tan A –tan B )/(1 + tan A*tan B). Now you have to REPLACE tan A and tan B for the values I gave you.

( 1/4 -1/5 )/( 1 + (1/4)(1/5))

( 5/20 -4/20 )/( (20/20) + (1/20))

( 1/20 )/( 19/20 )

20/380

1/19