Higher 2009

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Messages: 1 - 7 of 7
• Message 1.

Posted by U15219824 (U15219824) on Friday, 18th May 2012

Can someone help me please on q 7 on the 2009 paper 2? Thanks!

• Message 2

, in reply to message 1.

Posted by U15219824 (U15219824) on Friday, 18th May 2012

i know how to do a but not b! also does anyone know how to evaluate 5c as I get an answer of 399.2 every time i do it but i have all the right working and just cant get an answer of 12.4 as in the marking scheme.

Thanks

• Message 3

, in reply to message 2.

Posted by TigerLilidh (U15259229) on Saturday, 19th May 2012

Hi,
I'm stuck on those questions as well as 5b :/ I can get to the point where
cos2x = 3/7 but after that I'm baffled. Any help would be appreciated Thanks

• Message 4

, in reply to message 1.

Posted by Maths Teacher BBC (U15178780) on Sunday, 20th May 2012

This is a level A question:

(a) p.(q + r)
= p.q + p.r
= Mag P Mag Q cosƟ + 0
= 4 x 3 c cos 30
= 6√3

r.(p - q)
= r.p - r.q
= 0 - mag R mag Q cosƟ
= -3/2 x 3 x cos -60
= -9/2 x -1/2
= 9/4

(b) q + r = DE = √3² - (3/2)² = 3√3 /2

-q + r = AC = √(4 - 3√3 / 2)² + (3/2)²

• Message 5

, in reply to message 2.

Posted by Maths Teacher BBC (U15178780) on Sunday, 20th May 2012

5(C)

integrate between 0.6 and 2.6 -
-4cos2x + 3 - 3 cos 2x dx
= -7cos2x + 3 dx

-7/2 sin 2x + 3x between 2.6 and 0.6

= [-7/2 sin 2 x 2.6 + 3 x 2.6] - [ -7/2 sin 2 x 0.6 + 3 x 2.6]
= 10.98 - 1.46
= 12.35

• Message 6

, in reply to message 3.

Posted by Maths Teacher BBC (U15178780) on Sunday, 20th May 2012

5 (b)

cos 2x = 3/7

Solve this as normal for x - in RADIANS

In a CAST diagram it lies in A and C
x = 1.12788...
and
x = 2pi - 1.12788... = 5.1553...

However the question asks for 2x =
so
2x = 1.12788... and 5.1553....

x = 0.56396... and 2.577...

So to 1 decimal place
x = 0.6 and x = 2.6

The question asks for coordinates so substitute into the equations;

x = 0.6
y = 3cos(2x0.6) = 1.2

x = 2.6
y = 3cos (2x2.6) = 1.4

Points are then:

(0.6, 1.2) and (2.6, 1.4)

• Message 7

, in reply to message 6.

Posted by TigerLilidh (U15259229) on Sunday, 20th May 2012

Ta, that makes much more sense now

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