Exercise #18 notes

1. Exercise #18 Double Angle Identities sin 2  2sin  cos cos 2  cos 2   sin 2  OR  2cos   1 2  1  2sin 2  OR 2 tan  tan 2  1  tan 2  Example Evaluate cos120 using the double angle formula. Example 4 3 If sin   and cos  , find tan 2 . 5 5

2. Example Solve sin 2  sin  over the interval 0, 2  . Example     Given that cos    0.99 , evaluate cos   .  20   10  Try     Evaluate cos   given that cos    0.97 . 7  14 