| sin2x | cos2x | |||
(tgx + ctgx)2 = tg2x + 2tgxctgx + ctg2x = | + | + 2 = | ||
| cos2x | sin2x |
| sin4x + cos4x | (sin2x+cos2x)2 − 2sin2xcos2x | |||
= | + 2= | +2 = | ||
| sin2xcos2x | sin2xcos2x |
| 1 − 2sin2xcos2x | 1 | ||
+ 2 = | − 2 + 2 = | ||
| sin2xcos2x | sin2xcos2x |
| 1 | sin2x + cos2x | 1 | 1 | ||||
= | = | + | |||||
| sin2xcos2x | sin2xcos2x | cos2x | sin2x |