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How to do the eighth question in the math quality test paper of Taizhou Middle School in Jiangsu Province in March and September?
It's simple. . . . The analogy between the two fans came out. . . Look at the maximum area of each rectangle that bisects the second sector from the center line.

S =1/2 * r * r * tan (α *1/2) and then add the rectangles in the two sectors.

Results S=R*R*Tan(α* 1/2)