Question

Find the radius of the circle angle 90 A=20cm2

Answer 1

not sure if thets how you do it tho

Explanation:

Given, radius, r=20 cm, central angle, θ=90o, π=3.14

Area of sector =360oθ×πr2

=360o90o×3.14×20×20

=41×100314×20×20

=314

∴ the area of sector is 314 cm2.

Answer 2

Explanation:

I think you missed some things when posting the problem description.

did you mean to find the radius of a circle segment of 90 degrees and an area of 20 cm² ?

if that is the case :

remember, the area of a circle (a full circle of 360 degrees)

A = pi×r²

again, this is for the full 360 degrees.

how big is the area then for only a part of the circle ?

simply, it is the ratio of the angle of the segment compared to the total 360 degrees.

so,

As = pi×r² × angle/360

we have here

As = 20

angle = 90

20 = pi×r² × 90/360 = pi×r² × 1/4

80 = pi×r²

r² = 80/pi

r = sqrt(80/pi) = sqrt(16×5/pi) = 4×sqrt(5/pi) =

= 5.046265044 cm ≈ 5.05 cm