A lawn sprinkler sprays water up to 21 m and turns through 80°. Find the area of lawn it waters and the length of the curved edge of the watered patch. (Use π = 22/7)
How to lay out the answer. Follow the frame, then write it in your own words.
1 · Write what is given and what is to be found Given: r = 21 m, θ = 80°. To find: the area of the sector and its arc length.
2 · Draw the figure Point O for the sprinkler; two radii of 21 m with 80° between them; shade the sector.
3 · Write the formula or theorem Area of a sector = (θ/360) × πr². Arc length = (θ/360) × 2πr.
4 · Find the area Area = (80/360) × (22/7) × 21 × 21 = (2/9) × 1386 = 308 m².
