In order to prove

Let's write both sides in terms of
only.
Let's start with the left hand side: we can use the formula for sum and subtraction of the sine to write

and

So, their multiplication is

So, the left hand side simplifies to

Now, on with the right hand side. We have

Now simply make this expression one fraction:

And as you can see, the two sides are equal.
Answer:
D
Step-by-step explanation:
Associative property moves the parentheses, but the numbers stay in the same order.
Answer:
C. Equation: x=4
D. Slope: undefined
Step-by-step explanation:
If a line is perpendicular to the x-axis, then it is a vertical line because the x-axis is horizontal.
The slope of a vertical line is undefined.
The equation of a vertical line through
is 
Since the vertical line passes through (4,-2), its equation is

What diagram? There's no diagram.
Answer:
Step-by-step explanation:
4'7"<3