Question

R=−5sinθ+4θ

Which of the following types of symmetry is demonstrated in the equation above based on the three symmetry tests for polar equations?
θ=π/2
polar axis
pole
none

Answer 1

Answer: Correct answer is pie/2 or A

Explanation:

r = -5sinθ + 4θ has symmetry with respect to the line θ = π/2.

To demonstrate this, we can apply the third symmetry test for polar equations:

Symmetry with respect to the line θ = π/2: Replace θ by π - θ and see if the equation remains the same. If it does, the equation has symmetry with respect to the line θ = π/2.

r = -5sin(π/2 - θ) + 4(π/2 - θ) = 5cosθ + 2π - 4θ

r = 5cosθ + 2π - 4θ is the same as the original equation, so there is symmetry with respect to the line θ = π/2.

Therefore, the correct answer is θ = π/2.