Answer:
-1/2
Step-by-step explanation:
cos(x+pi) = -cos(x), so the answer is -1/2.
All the angles should add up to 360°.
8x+10x+9+21x-12+90=360°
Group like terms together.
So,8x+10x+21x+9+90-12=360
39x+87=360
39x=360-87
39x=273
x=7
z ≤ 8
z is less than or equal to 8
z is no more than 8
