ΠΠ½Π°ΡΡΠ°ΡΠΈΡ8 Π»Π΅Ρ Π½Π°Π·Π°Π΄
2sin^2(x) - 4sin(x)cos(x) + 4cos^2(x) = 1.
ΠΡΡΠ°Π·ΠΈΠΌ Π΅Π΄ΠΈΠ½ΠΈΡΡ ΡΠ΅ΡΠ΅Π· ΠΎΡΠ½ΠΎΠ²Π½ΠΎΠ΅ ΡΡΠΈΠ³ΠΎΠ½ΠΎΠΌΠ΅ΡΡΠΈΡΠ΅ΡΠΊΠΎΠ΅ ΡΠΎΠΆΠ΄Π΅ΡΡΠ²ΠΎ:
1 = sin^2(x)+cos^2(x).
ΠΠΎΠ΄ΡΡΠ°Π²ΠΈΠΌ Π² ΡΡΠ°Π²Π½Π΅Π½ΠΈΠ΅:
2sin^2(x) - 4sin(x)cos(x) + 4cos^2(x) = sin^2(x)+cos^2(x).
ΠΡΠΈΠ²Π΅Π΄ΡΠΌ ΠΏΠΎΠ΄ΠΎΠ±Π½ΡΠ΅ ΡΠ»Π°Π³Π°Π΅ΠΌΡΠ΅:
2sin^2(x) - sin^2(x) - 4sin(x)cos(x) + 4cos^2(x) - cos^2(x) = 0
sin^2(x) - 4sin(x)cos(x) + 3cos^2(x) = 0.
ΠΡΠ΅Π΄ΡΡΠ°Π²ΠΈΠΌ Π²ΡΡΠ°ΠΆΠ΅Π½ΠΈΠ΅ 4sin(x)cos(x) ΠΊΠ°ΠΊ [sin(x)cos(x) + 3sin(x)cos(x)], ΠΏΠΎΠ΄ΡΡΠ°Π²ΠΈΠΌ Π² ΡΡΠ°Π²Π½Π΅Π½ΠΈΠ΅:
sin^2(x) - [sin(x)cos(x) + 3sin(x)cos(x)] + 3cos^2(x) = 0.
Π Π°ΡΠΊΡΠΎΠ΅ΠΌ ΡΠΊΠΎΠ±ΠΊΠΈ, ΡΡΠΈΡΡΠ²Π°Ρ ΡΠΌΠ΅Π½Ρ Π·Π½Π°ΠΊΠΎΠ²:
sin^2(x) - sin(x)cos(x) - 3sin(x)cos(x) + 3cos^2(x) = 0.
ΠΡΠ½Π΅ΡΠ΅ΠΌ Π·Π° ΡΠΊΠΎΠ±ΠΊΠΈ ΠΎΠ±ΡΠΈΠ΅ ΠΌΠ½ΠΎΠΆΠΈΡΠ΅Π»ΠΈ sin(x) ΠΈ 3cos(x):
sin(x)*[sin(x) - cos(x)] - 3cos(x)*[sin(x) - cos(x)] = 0.
ΠΡΠ½Π΅ΡΠ΅ΠΌ Π·Π° ΡΠΊΠΎΠ±ΠΊΠΈ ΠΎΠ±ΡΠΈΠΉ ΠΌΠ½ΠΎΠΆΠΈΡΠ΅Π»Ρ [sin(x) - cos(x)]:
[sin(x) - cos(x)]*[sin(x) - 3cos(x)] = 0.
Π Π΅ΡΠΈΠΌ ΡΡΠ°Π²Π½Π΅Π½ΠΈΡ sin(x) - cos(x) = 0 ΠΈ sin(x) - 3cos(x) = 0:
1)sin(x) - cos(x) = 0,
sin(x) = cos(x).
Π Π°Π·Π΄Π΅Π»ΠΈΠΌ ΠΎΠ±Π΅ ΡΠ°ΡΡΠΈ ΡΡΠ°Π²Π½Π΅Π½ΠΈΡ Π½Π° cos(x):
sin(x)/cos(x) = cos(x)/cos(x).
Π‘Π΄Π΅Π»Π°Π΅ΠΌ Π·Π°ΠΌΠ΅Π½Ρ sin(x)/cos(x) = tg(x):
tg(x) = 1,
x = Ο/4+Οk.
2)sin(x) - 3cos(x) = 0,
sin(x) = 3cos(x).
Π Π°Π·Π΄Π΅Π»ΠΈΠΌ ΠΎΠ±Π΅ ΡΠ°ΡΡΠΈ ΡΡΠ°Π²Π½Π΅Π½ΠΈΡ Π½Π° cos(x):
sin(x)/cos(x) = 3cos(x)/cos(x).
tg(x) = 3.
x = arctg3 + Οk.
ΠΡΠ²Π΅Ρ: x1 = Ο/4+Οk, x2 = arctg3 + Οk.