扇形弧长=r*α圆锥的底半径=扇形弧长/（2π）=r*α/(2π）圆锥底面积=π*圆锥的底半径²=（r*α）²/(4π)圆锥高²=r²-圆锥的底半径²=r²-(r*α/(2π）)²=r²（1-α²/（4π...