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CHAPTER 4
AOB is a sector of a circle with centre at O and radius 2cm. Find the area
Example 1
of the shaded region.
OPERATION
1. First enter Rad (radian) mode.
MODE
MODE
2. Calculate the area of sector using the formula
b
1
a
/
2
c
DGRÈ
Ans
X
1
3. Now calculate the area of the triangle AOB using the formula
b
a
/
1
2
c
sin
6
0
4 . The area of the shaded region is
–
RCL
M+
Therefore, the area of shaded region is approximately 0.3623cm
sign.
Show that the length of arc AB in the above example is approximately 2.0944cm.
SHIFT
Press
0
Circular Measure
2
X
6
0
=
2
2
x
2
X
2
x
DGRÈ
SHIFT
Ans
1
=
STO
M
to clear the memory stored in M.
M+
RCL
A
2cm
O
60°
2cm
B
1
2
θ
r
and store the calculated result.
2
SHIFT
1ª2X 60– X2
M+
1
2
θ
r
sin
2
X
1ª2X2
=
Ans-M
2
, ignoring the negative
R
0
2
2.094395102
.
2
X sin 60–
1.732050808
-0.362344294
13
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