If it takes 9 yards of material to make curtains for 3 windows, how much material is needed for 11 windows?

33 material

Step-by-step explanation:

A simple proportions problem.

9:3 = 3:1

so it takes 3 yards to make 1 window

We multiply both sides by 11 to get

33:11 which now we get 33 material

C

Step-by-step explanation:

In a trigonomitrical circle

● cos x => x

● sin x => y

So

● sin x /(cos^2 x - sin^2 x) = y/y^2-x^2

A cartesian from start with y=

So y = x^2 -y^2