Answer:
A.
Step-by-step explanation:
You have the following expression:

To verify the identity, you have that the left side of the equation becomes:
(1 + cosx)(1 - cosx) = (1 - cos^2 x)
because of the product of an expression by its conjugate result in a difference of squares. Or simplfy by expanding the factors and simplying.
Next, you have:
1 - cos^2 x = sin^2 x
because the Pythagorean identity.
Then, the identity is verified.
Hey there!
12 decreased by twice a number is -34.
Decreased= -
Twice=2
Number=n
2n-12= -34
I hope this helps!
~Kaikers
Start here: A = 18 ft^2 = L * W. Next, L = 2W.
Merging these 2 formulas lets us eliminate L:
18 ft^2 = (2W) * (W) = 2W^2.
So W^2 = 9 ft^2, and W=3 ft. Please use L = 2W (from above) to calculate L.