9 dollars is 4 dollars.
Let's find the percent form of the discount
=> 4 dollars / 9 dollars = 0.44
Now, let's convert it to percentage
=> 0.44 * 100% = 44%
Thus the discount is 44%
Marco's equation is correct. Cosine is an even function, which means that for every x, f(-x) = f(x). In other words, you get the same answer for a negative value that you would for its corresponding positive value.
