A) 2Sin(x + y) - 3Cos(x - y) = 5|*5 10Sin(x + y) -15Cos(x - y) = 25
5Sin(x + y) + 7Cos(x - y) = 2 |*(-2), ⇒ -10Sin(x + y) -14Cos(x - y) = -4
сложим почленно, получим:
-29Cos(x - y) = 21
Cos(x - y) = -21/29
x- y = +-arcCos(-21/29) + 2πk , k ∈Z
б) 2Sin(x + y) - 3Cos(x - y) = 5|* 7 14Sin(x - y) -21Cos(x + y) = 35
5Sin(x + y) + 7Cos(x - y) = 2 |* 3, ⇒ 15Sin(x + y) +21Cos(x - y) = 6
сложим почленно, получим:
29Sin(x + y) = 41
Sin(x + y ) = 41/29> 1
∅