Question

Calculator question.

Answer 1

Answer:

D. [0,pi/2]

Step-by-step explanation:

when Ф = 0 in radian

r²=  4cos (2(0))

r² = 4 * 1

r² = 4

∴ r = √4 = 2

r = 2.

when Ф = π/2 in radian

r²=  4cos (2(π/2))

r² = 4 * -1

r² = -4

∴ r = 0