| cos ( 270° + α) =
|
A. sin α |
|---|
| B. cos α |
| C. − cos α |
| D. − sin α |
| E. geen v.d. vorige |
[ 4,5-3394 - op net sinds 20.12.02-(E)-30.10.2023 ]
Translation in E N G L I S H
|
cos ( 270° + α) =
|
A. sin α |
|---|
| B. cos α |
| C. − cos α |
| D. − sin α |
| E. none of the above |
Oplossing - Solution
1ste manier :
cos(270°+α) = - cos(90°+α) = − sin[90°−(90°+α)] = − sin(90° − 90° − α) = −sin(−α) = sin α
2de manier :
cos(270°+α) = cos(−90°+ α) = cos(90°− α) = sin α
3de manier :
cos(270°+α) = −cos[180°−(270°+α)] = −cos(180°−270°− α)= −cos(−90°− α)
= −cos(90°+ α) = − sin[90°−(90°+α)] = − sin(90° − 90° − α) = −sin(−α) = sin α
