A) The distance to the right is a weird expression. It's either distance in the horizontal direction from the center or it's displacement to the right (that allows values that are <0 to the left) or it is unstated that we are limited to the first quadrant. If the first is meant, then the distance away from the center horizontally is |rcosθ|.
B) x = rcosθ = 2.5cosθ
C) plug in and make sure your calculator is in radians. (3.9 radians is obviously greater than π/2, so we are not limited to the first quadrant.
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