Hello,
A)
cos 135°=- cos 45°=-√2/2
sin 135°=sin45°=√2/2
2(cos 135°+i sin 135°)=-√2 + i*√2
B)
cos 120°=-cos 30°=-√3 /2
sin 120°=sin 30°=1/2
3(cos 120° + i sin 120)=-3/2*√3 +i*3/2
C)
cos (5π/4)=-cos (π/4)=-√2 /2
sin (5π/4)= -sin(π/4)=-√2 /2
5(cos (5π/4)+i sin (5π/4))=-5/2*√2 +i *5/2*√2
D)
cos(5π/3)=cos(π/3)=√3 /2
sin (5π/3)=-sin(π/3)=-1/2
4(cos(5pi/3)+i sin (5pi/3))
=2√3- 2*i
Step-by-step explanation:
multiply the first equation by 1, the second by -1 and add.
x + 2y = -16
-x - 6y = 28
--------------------
0 - 4y = 12
-4y = 12
y = -3
x + 2×-3 = -16
x - 6 = -16
x = -10
