help with a trig function (1 Viewer)

[Ellis]

Hi, can anyone help to answer this question? I was taught this way today, I obviously haven't done it correctly though, the solution is the same except
-cos^2 where I wrote sin^2.


Thanks

 

[Kurosaki]

they used u=cos(x) as a substitution. Your answer is still correct however.
The reason is because , and the half gets sucked up into the constant.

Edit: also the dx in the second last line should be a du

 

[Shadowdude]

Hi, can anyone help to answer this question? I was taught this way today, I obviously haven't done it correctly though, the solution is the same except
-cos^2 where I wrote sin^2.
View attachment 30119

Thanks

When you let , you get:



Your mistake is then substituting 'dx' for 'du'. (i.e. fifth line)

Moreover, you wrote where it should technically be because you "substituted" 'du' in.


Try letting .

 

[Ellis]

Ah right, that makes sense now, thanks a lot