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Title: Cambridge International Examination,General certificate of Education,Advanced Subsidiary level P2 Pure maths, October/November,university Of Cambridge Local Examination Syndicate
Description: Cambridge International Examination General Certificate of Education Advanced Subsidiary Level Mathematics Paper 2 Pure mathematics (P2) OCTOBER / NOVEMBER SESSION 2001 University Of Cambridge Local Examination Syndicate

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Cambridge International Examination
General Certificate of Education Advanced Subsidiary Level
Mathematics
Paper 2 Pure mathematics (P2)
OCTOBER / NOVEMBER SESSION 2001
University Of Cambridge
Local Examination Syndicate

Show that ∫

Q7(i)

πœ‹

πœ‹

4

1
4
and that ∫
2
0

sin2x dx =

0

(ii) Use the result in part (i) to evaluate

Now ∫
= 2∫

πœ‹
4
0

0

πœ‹
4

(2sinx + 3cosx) 2 dx

0

Solution (i)
Since sin2x = 2sinxcosx
d
Also
sinx = cosx
dx
d(sinx) = cosx dx
sin2xdx = ∫

πœ‹
4

∫

sinx d(sinx) = 2

πœ‹
4

0

2sinxcosx dx = 2∫
πœ‹

πœ‹
4
0

sinx (cosxdx)

πœ‹

4

(sinx) 2
2

1
cos 2 x dx = (πœ‹ + 2)
8

= (sinx) 2

4
0

= sin

0

πœ‹

2

4

-

(sin0) 2

2

2

=

-0 =

2

1
2

πœ‹

1
2
Also cos2x = cos x - sin 2 x ------------ (1)
sin 2 x + cos 2 x = 1
⟹ sin 2 x = 1 - cos 2 x ------------ (2)
From equation (1) and equation (2)
cos2x = cos 2 x - 1 - cos 2 x = cos 2 x - 1 + cos 2 x = 2cos 2 x - 1
Hence ∫

4

0
2

sin2x dx =

cos2x + 1 = 2 cos 2 x
1 + cos2x
= cos 2 x
2
πœ‹
πœ‹
πœ‹
πœ‹
1 4
1 4
4
4 1 + cos2x
⟹∫
cos 2 xdx = ∫
dx = ∫ dx + ∫ cos2x dx
0
0
2
2 0
2 0
πœ‹

πœ‹

1
1 sin2x
= [x] 04 +
2
2
2
=

πœ‹
8

+

4

=
0

1 πœ‹ 1
πœ‹
+
sin2
- sin2(0)
2 4 4
4

1
πœ‹
πœ‹ 1
πœ‹ 2
sin - sin(0) =
+ ( 1) =
+
4
2
8 4
8 8
⟹∫

πœ‹
4

0

1
cos 2 x dx = ( πœ‹ + 2)
8

(ii)

I=∫

πœ‹
4
0

(2sinx + 3cosx) 2 dx

------------ (1)

Now (2sinx + 3cosx) 2 = 4sin 2 x + 9cos 2 x + 12sinxcosx
= 4sin 2 x + 9cos 2 x + 6 (2sinxcosx) --------- (2)
Also
sin 2 x + cos 2 x = 1
2
⟹ sin x = 1 - cos 2 x ----------- (3)
2sinxcosx = sin2x --------------- (4)
Putting equation (3) & equation (4) in equation (2)
(2sinx + 3cosx) 2 = 4 1 - cos 2 x + 9 cos 2 x + 6 sin2x
= 4 - 4cos 2 x + 9cos 2 x + 6sin2x
= 4 + 5cos 2 x + 6sin2x ---------- (5)
Putting equation (5) in equation (1)
I=∫

πœ‹
4

0

4 + 5cos 2 x + 6sin2x dx

= 4∫

πœ‹
4
0

dx + 5∫

πœ‹

=4
= πœ‹ + 5∫

Putting ∫

I=∫

4
πœ‹
4
0

+ 5∫

0

0

4
0

πœ‹
4

0

cos 2 x dx + 6∫

cos 2 x dx + 6 ∫

cos 2 x dx + 6∫

cos 2 x dx + 6∫

πœ‹
4

4

πœ‹

πœ‹

= 4 [x] 04 + 5∫

πœ‹

4

4
0

4
0

sin2x dx

πœ‹
4
0

4
0

sin2x dx

πœ‹

sin2x dx

sin2x dx ----------- (6)

πœ‹

cos 2 x dx =

1
1
4
(πœ‹ + 2) and∫ sin2xdx = in equation (6)
8
0
2

πœ‹
0

πœ‹

πœ‹

(2sinx + 3cosx) 2 dx = πœ‹ + 5

=

1
1
5πœ‹ 10
( πœ‹ + 2) + 6
= πœ‹+
+
+3
8
2
8
8

13πœ‹ 34
+
8
8


Title: Cambridge International Examination,General certificate of Education,Advanced Subsidiary level P2 Pure maths, October/November,university Of Cambridge Local Examination Syndicate
Description: Cambridge International Examination General Certificate of Education Advanced Subsidiary Level Mathematics Paper 2 Pure mathematics (P2) OCTOBER / NOVEMBER SESSION 2001 University Of Cambridge Local Examination Syndicate