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#26 Re: Help Me ! » quadratics » 2005-12-13 12:46:47

Good point. I think only Anastasia can clear that out ...

#27 Introductions » Hi » 2005-12-13 02:51:49

Chemist
Replies: 3

Hello fellow Mathematicians & non-Mathematicians,
As I'm new to the forum, I thought to introduce myself. Obviously, I'm majoring in chemistry , and I'm still in my 1st semster. I'm currently taking Calculus III & Analytical geometry as well as Statistics & probability.
There are two more Math courses to go during the next 2 semesters,  so I'm counting on you geniuses.

#28 Re: Help Me ! » quadratics » 2005-12-13 02:30:41

Yes you're right , I apologize for my mistake, for x=0, y=1. Isn't a vertex considered like an intersection point btw?

#29 Re: Help Me ! » Integration » 2005-12-12 22:31:44

Greetings Flowers4Carlos,
Thank you for your help. I believe there's no mistake in your calculation, which is pretty good and simple. I shall double check the answer anyhow, thanks again.

#30 Re: Help Me ! » quadratics » 2005-12-12 12:33:49

you mean finding the roots of this quad eq ?

General formula :
ax^2 + bx + c = 0

First find Delta Δ = b^2 - 4ac
x1 = ( -b + √Δ ) / 2a

x2 = ( -b - √Δ ) / 2a

If b is even , you can take delta = b^2 - ac , if i remember correctly, and instead of 2a, u use a in the denominator.

Anyway the roots should be :

x1 =  - 0.29
x2 = -1.7

Concerning the intercepts, just equate x and y to 0 for a general equation. In this case, this is a parabola, so the roots found are x intercept and the y intercept is 0.

#31 Re: Help Me ! » Integration » 2005-12-12 12:14:13

No problem mate, I'll try out different methods. Thanks anyway.

#32 Re: Help Me ! » Integration » 2005-12-12 12:04:13

Hello mathsyperson ,

thank you for your help, but you obviously didnt notice the / ( division ). The exp is (1 + cosθ) / (1 - cosθ). This is why I changed it to TanB/2

#33 Help Me ! » Integration » 2005-12-12 10:38:14

Chemist
Replies: 7

Greetings mates,

If anyone can help me solve the following integral using the change of variable ჯ = cosმ

The ^ means to the power, so 2Cos^2მ is 2 multiplied by the squared of Cosმ ( just to avoid confusion ).

The given integral is:
I = ∫[(1+ჯ)/(1-ჯ)]^½dჯ

I already worked it out using other methods like taking t^2 = (1+ჯ)/(1-ჯ) and then solving in terms of t. I found out the solution. However, the method of change of variable using Cosმ is not working. For starters,

I = ∫[(1+cosმ)/(1-cosმ)]^½dcosმ = - ∫[(2Cos^2B)/(2Sin^2B)]^½ sinმdმ where B = მ/2

This implies, I = - ∫[1/|Tan^2B|] sinმdმ
--> I = - ∫ (sinმdმ / Tan^2B )

How to cotinue from here? I've tried many methods using integrations by parts, by nothing worked out.

Thanks in advance.

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