Saved Bookmarks
| 1. |
Proved that formula cos^2a - sin^2b = cos(a+b) |
|
Answer» ong>Answer: Step-by-step EXPLANATION: cos(a+b)cos(a-b) = (COSACOSB-sinasinb)(cosacosb+sinasinb) =(cosacosb)^2-(sinasinb)^2 =cos^2a cos^2b - sin^2a sin^2b =cos^2a (1-sin^2b) - (1-cos^a) sin^2b =cos ^2a -sin^2b |
|