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## #1 2009-03-13 17:32:28

ganesh
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### Level of Difficulty - III Questions.

1. If the sides of a triangle are in Arithmetic Progression, then find the value of

in terms of
.

2. A circle is inscribed in an equilateral triangle of side a. Find the area of the square inscribed in this circle.

3. Find the general value of θ satisfying the equation
tan2θ + sec2θ = 1.

4. Solve the equation
sin x - 3sin 2x + sin 3x = cos x - 3cos 2x + cos 3x.

Character is who you are when no one is looking.

## #2 2009-03-15 23:43:26

ganesh
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### Re: Level of Difficulty - III Questions.

5. Find the area bounded by the curve x2=4y and the
straight line x = 4y - 2.

6. If a, b, c are the three sides of a triangle and C = 60°, prove that

7. If a>0, b>0, and c>0, prove that
.

8.Find the equations of straight lines passing through (-2, -7) and having an interept of length 3 between the striaght lines
4x+3y = 12 and 4x+3y = 3.

Character is who you are when no one is looking.

## #3 2009-03-16 03:42:32

JaneFairfax
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### Re: Level of Difficulty - III Questions.

Q: Who wrote the novels Mrs Dalloway and To the Lighthouse?

## #4 2009-03-16 05:13:59

ganesh
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### Re: Level of Difficulty - III Questions.

Correct, JaneFairfax!

Character is who you are when no one is looking.

## #5 2009-03-17 02:06:18

ganesh
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### Re: Level of Difficulty - III Questions.

9. For what values of m does the system of equations
3x + my = m and
2x - 5y = 20
have solutions satisfying the condtions x>0, y>0?

10. Let -1 ≤  p ≤  1. Show that the equation 4x3 - 3x - p = 0 has a unique root in the interval [½, 1] and identify it.

Character is who you are when no one is looking.

## #6 2009-04-14 04:25:37

bobbym

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### Re: Level of Difficulty - III Questions.

Hi Ganesh;
For #9

Solve for x and y in terms of m to understand how x and y behave when m varies:

After a lot of algebraic thrashing and some trial and error:

These values of m satisfy the constraints x>0 and y>0

Last edited by bobbym (2009-04-14 04:38:13)

In mathematics, you don't understand things. You just get used to them.
90% of mathematicians do not understand 90% of currently published mathematics.
I am willing to wager that over 75% of the new words that appeared were nothing more than spelling errors that caught on.

## #7 2009-04-21 13:35:26

bitus
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### Re: Level of Difficulty - III Questions.

#1: tan(A/2) +tan(C/2) = (2/3)cot(B/2)

#4: x=pi/8 or 3pi/8

## #8 2009-04-21 14:56:34

bitus
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### Re: Level of Difficulty - III Questions.

#6 : cosC=1/2⇒b² -(b/2)²=c² -(a-b/2)² ⇒ab=a²+b²-c² ⇒3ab=(a+b)² -c²a+b+c)(a+b-c)a+b+c)(a+b+c-2c)=
(a+b+c)²-2c(a+b+c)⇒3ab+2c(a+b+c)a+b+c)²⇒3ab+3c(a+b+c)a+b+c)²+c(a+b+c)⇒
3(a+c)(b+c)a+b+c)(b+c+a+c)⇒[(b+c)+(a+c)]/(a+c)(b+c)=3/(a+b+c)⇒1/(a+c)+1/(b+c)=
3/(a+b+c).

## #9 2009-04-21 20:44:35

bobbym

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### Re: Level of Difficulty - III Questions.

Hi bitus,

For #4 I think you mean

doesn't work when I plug it in.

In mathematics, you don't understand things. You just get used to them.
90% of mathematicians do not understand 90% of currently published mathematics.
I am willing to wager that over 75% of the new words that appeared were nothing more than spelling errors that caught on.

## #10 2010-05-17 17:26:06

BO
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### Re: Level of Difficulty - III Questions.

1.from sine rule we get sinA+sinC=2sinB, or cos([A-C]/2)=2cos(B/2)
tan(A/2)+tan(c/2)=cos(B/2)/[cos (A/2) cos (C/2)]=2cos(B/2)/[sin(B/2)+2cos(B/2)]=2/[1+cot (B/2)]

Then the diameter of the square=2a/3
area=(2a/3 sin45)^2=a^2/9

Last edited by BO (2010-05-17 17:32:48)

BO
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3. tan θ=1/2

## #12 2010-05-22 01:03:22

irspow
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### Re: Level of Difficulty - III Questions.

Last edited by irspow (2010-05-22 01:04:34)

## #13 2010-05-22 22:34:14

ganesh
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### Re: Level of Difficulty - III Questions.

Well done,
irspow!!!

Character is who you are when no one is looking.