| √5 | ||
W trój. prost. o kątach ostrych α i β zachodzi warunek: cos α + cos β = | . Oblicz | |
| 2 |
| 5 | ||
wychodzi cos2 α + cos2 β = | . Co dalej  | |
| 4 |
| 5 | ||
czy może cos2 α + 2cosαcosβ + cos2 β = | | |
| 4 |
| √5 | ||
(cos α + sin α )2 = ( | )2 | |
| 2 |
| 5 | ||
cos2α + 2 cos α*sin α + sin2α = | ||
| 4 |
| 5 | 1 | |||
2 sinα*cos α = | − 1 = | / : 2 | ||
| 4 | 4 |
| 1 | ||
sin α*cos α = | oraz cos α = sin β | |
| 8 |
| 1 | ||
sinα*sin β = | ||
| 8 |
