Finding the Solution: Solving for [sin(alpha)]^2 in a Complex Equation

[alexolcz]

Hi I was wondering if anybody could help solve this equation. I have the answer but i can't seem to work out how my teacher arrived at this,

Many thanks
Alex

Homework Statement

alpha
A = constant

Homework Equations

Solve for [sin(alpha)]^2

A^2- [sin(alpha)]^2*(A^2+2)+2*[sin(alpha)]^4

The Attempt at a Solution

The solution is given as

[sin(alpha)]^2 = (A^2)/2 or 1

 

[tiny-tim]

Welcome to PF!

Hi Alex! Welcome to PF!

(try using the X² tag just above the Reply box )

So you mean solve A² - B(A² + 2) + 2B² = 0 for B?

 

[alexolcz]

Hi,

Thanks for your fast reply, sorry about the formatting I'm new to all this!

Yes that the question. I realize that it is basically a simple quadratic but when i try to solve it using to the quadratic formula I don't end up with the required results?

Thanks again

Alex

 

[berkeman]

Hi,

Thanks for your fast reply, sorry about the formatting I'm new to all this!

Yes that the question. I realize that it is basically a simple quadratic but when i try to solve it using to the quadratic formula I don't end up with the required results?

Thanks again

Alex

Please post your work, so we can see where you are going wrong...

 

[alexolcz]

Hi,

I've just manage to solve it! Thanks for your offers of help, very kind.

Merry Christmas

Alex