- #1
Pomico
- 25
- 0
This is a step from my notes that I don't follow. I have sin[tex]\theta[/tex][tex]\frac{d}{d\theta}[/tex](sin[tex]\theta[/tex][tex]\frac{d\Theta}{d\theta}[/tex]) and that, when substituting u=cos[tex]\theta[/tex] and writing that [tex]\Theta[/tex]([tex]\theta[/tex])=P(u), [tex]\frac{d}{du}[/tex]((1-u[tex]^{2}[/tex])[tex]\frac{dP}{du}[/tex]) is obtained.
I can see [tex]\frac{d\Theta}{d\theta}[/tex]=[tex]\frac{dP}{du}[/tex] for the far RHS but can't get the 1-u[tex]^{2}[/tex] to come out. I don't really remember how to do this though I'm sure I have been able to at some point so a starting tip would be much appreciated! The main trap I keep falling in is the temptation to try something with chain rule to get rid of all those d[tex]\theta[/tex] bits in the original equation. I know I'm not supposed to as I'm just supposed to be substituting, not solving, but I'm not sure how else to go about it.
I can see [tex]\frac{d\Theta}{d\theta}[/tex]=[tex]\frac{dP}{du}[/tex] for the far RHS but can't get the 1-u[tex]^{2}[/tex] to come out. I don't really remember how to do this though I'm sure I have been able to at some point so a starting tip would be much appreciated! The main trap I keep falling in is the temptation to try something with chain rule to get rid of all those d[tex]\theta[/tex] bits in the original equation. I know I'm not supposed to as I'm just supposed to be substituting, not solving, but I'm not sure how else to go about it.