| −5√39 | ||
Wiedząc, że sinαcosα= | i α∊(90; 180), oblicz cos2α. | |
| 64 |
| 5√39 | ||
sin α*cos α = − | /*2 i α ∊ ( 90o, 180o) | |
| 64 |
| 5 √39 | ||
2 sinα α *cos α = − | ||
| 32 |
| 5 √39 | ||
sin 2α = − | ||
| 32 |
| 25*39 | 1024 − 975 | 49 | ||||
cos2 2α = 1 − | = | = | ||||
| 322 | 322 | 322 |
| 7 | ||
cos 2α = | ||
| 32 |