Question

Which of the following describes the graph of the polar equation rcosθ = 4?

horizontal line through -4
vertical line through -4
horizontal line through 4
vertical line through 4

Answer 1

keeping in mind that 

y = rsin(θ)
x = rcos(θ)

then rcos(θ) = 4, is really in rectangular the same as x = 4.  Check the picture below.