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Mathematics: Post your doubts here!

R_Ma7mooD

R_Ma7mooD

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anyone can explain how to answer B)
Photo%2012-23-14%2C%206%2032%2015%20PM.jpg

:D
 
W

Wolfgangs

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Guys, I have taken Mathematics AS levels in the May/June session in 2013 with the P1 and S1 combination. I scored 'a' in Mathematics AS levels and I think my mark is 105/125. In the A levels, I'm taking P3 and M1, what are my chances of scoring A* or how many marks do I need to score A*?
 
The Sarcastic Retard

The Sarcastic Retard

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Wolfgangs said:
Guys, I have taken Mathematics AS levels in the May/June session in 2013 with the P1 and S1 combination. I scored 'a' in Mathematics AS levels and I think my mark is 105/125. In the A levels, I'm taking P3 and M1, what are my chances of scoring A* or how many marks do I need to score A*?
Click to expand...
Depends on thresholds. Normally, for an A* you should score 90% or plus. As you are math student count yourself how much marks are required to break that 90%. Good luck.
 
Sarosh Jameel

Sarosh Jameel

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  1. PLZ HELP ME WITH THE QUESTION 5 !!
 

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H

huh

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Sarosh Jameel said:
  1. PLZ HELP ME WITH THE QUESTION 5 !!
Click to expand...

(sin)4-(cos)4
=((sin)2+(cos)2)((sin)2-(cos)2)
=(sin)2-(1-(sin)2)
=(sin)2-1+(sin)2
=2(sin)2-1

2(sin)2-1=0.5
(sin)2=0.75
Angles: 60, 120, 300, 240

Sorry for the poor representation, but hopefully you can understand.
 
The Sarcastic Retard

The Sarcastic Retard

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Sarosh Jameel said:
  1. PLZ HELP ME WITH THE QUESTION 5 !!
Click to expand...
Let theta be x,
Part i)
sin^4x - cos^4x
= (sin^2x)(sin^2x) - (cos^2x)(cos^2x)
= (sin^2x)^2 - (cos^2x)^2
We know a^2 - b^2 = (a - b)(a + b)
= (sin^2x - cos^2x)(sin^2x + cos^2x)
We know sin^2x + cos^2x = 1
= (sin^2x - cos^2x)(1)
= sin^2x - cos^2x
sin^2x - cos^2x
= sin^2x - (1 - sin^2x)
= 2sin^2x - 1
Part ii)
sin^4x - cos^4x = 2sin^2x - 1
2sin^2x - 1 = 1/2
2sin^2x = 3/2
sin^2x = 3/4
sin(x) = (Roof of 3)/2
x = 60
As x lies between 0 to 360, there will be more 3 values of x.
x = 60 ; (180 - x) = (180 -60) = 120
x = 60 ; (x + 180) = (60 + 180) = 240
x = 120 ; (x +180) = (120 + 180) = 300
Therefore, x = 60, 120, 240, 300.
 
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