It reads: When you rotate the x-y coordinate system by an angle of , the new cordinates x' and y' can be calculated using the following expressions:

x'= xCos + ysin (1)

y'=-xsin + ycos (2)

Given that you know the rotated coordinates x' and y' and the rotation angle how do you calculate the original x an y? (in other words, how do you express x and y using x', y' and ?

Hint: rearrange equations (1) and (2) so that x and y can be expressed using x', y', sin and cos

and thats all it gives me except for the addition of another example problem which asks

if x'=24, y'=-3 and =30 degrees, what are the values of x and y?

many thanks, also what are these problems trying to show im not really sure what they have to do with college algebra.