圓形的數題

1.
In fact, the angle of the sector can be in radian form or degree form.
First, for the degree form,
Let a be the angle of the sector
As a whole circle with radius 6cm has 2π(6) cm,
then a/360° * 2 π(6)=20
a=191°(correct to the nearest degree)
The angle of the sector is 191°

On the other hand, we can get the angle in radian form
If you have studied in A. Maths, then you will get
the perimeter of sector= ra, where a is the angle of sector in radian form
Then 6a=20
a=3.33 rad (correct to 2 d.p.)
In addition, if you change radian into degree, you can insert into the calculator to get the answer(since different calculators will have different method to insert, I will suggest you to read the instruction of the calculator)

2.Since you haven't posted the figure which can show the shaded part of the prism, without enough information, we can't deduce the answer with only the height of prism.Could you please post it on the net, or send a message to me from profile ( press 寄信給他/她)? Thank a lot!

1. (20-12) / 3.14 / (6 * 2) * 360 = 76

1. 76.43 =2*3.14*radius *angle /360=length of arc

length of arc = 20- radius- radius = 8

The angle of sector =

2*3.14*6*degree/360=8

so the angle is 76.43

2. I don't know
you information is not enough for solve your problem