Suppose we have a circle whose radius is 5cm. If a sector of this circle has an area of 15 cm^2, what is the size its angle (in degrees)?
Firstly, you would need to figure out what formula you can use to solve this problem. You know the radius and area of the sector, and you need to find the angle. So, the correct equation to use would be the formula for the area of a sector: A = θ/360 x πr2 . Substituting 15 for A and 5 for r, we have 15 = θ/360 x 25π. We then want to make θ the subject of our equation, so we need to multiply both sides by 360, and then divide both sides by 25π. Finally, we have our solution: θ = (15x360)/25π = 68.8 (in 3 s.f.).
