∏r+2r= ∏r×∏r2∏r+4r=∏r×∏r6.28r+4r=3.14×r×r10.28=3.14rr≈3.27这道题我做过,当时我想了好长时间呢!
设半径为X 1/2X*X*3.14=3.14X+2X
半径为r1/2×3.14×r=3.14r+2rr=514/157