f.2 maths difficult

1.
Let radius of cake = r, height of cake = h.
so volume of cake = pr^2h = 300 or prh = 300/r..........(1) p = pi
Curved surface area = 2prh = 2(300/r) = 600/r. [From (1)]
so possible value of curved surface area depends on possible values of radius, r.
2.
Each interior angle of a regular n-sided polygon = [(n -2) x 180 ]/n
now n = 8, so each interior angle = 6 x 180 /8 = 135 degree.
so angle with grass = 360 - 135 = 225 degree.
Now radius = 3, so area of sector = p x 3^2 x 225/360 = 5.625p m^2.
= 17.7 m^2 ( 3 sig. fig.)

1.
設r cm是蛋糕的半徑,h cm是蛋糕的高
pi r^2 h =300
prh = 300/r

曲面面積=2prh
=2(300/r)
=600/r cm^2

∴該蛋糕的曲面面積是600/r cm^2

2.
正八邊形的內角=[(8 -2) x 180 ]/8
=135°
該牛可以吃草的最大範圍的面積= pi×3^2×(360-135)°/360°
= pi×3^2×225°/360°
=5.625pi m^2
或=17.7 m^2 ( corr to 3 sig. fig.)