# Thread: Find x values of stationary points

1. ## Find x values of stationary points

Find the values of x at the stationary points for sin(x^2)

I found the 1st derivative which is 2xcos(x^2)

I know the final answer is x = 0 and x = \pm sqrt((k+(1/2))pi) for k = 0,1,2....

How do you get that answer?? I can see how the answer is x = 0, but how do you figure out the other one?

2. Originally Posted by brumby_3
Find the values of x at the stationary points for sin(x^2)

I found the 1st derivative which is 2xcos(x^2)

I know the final answer is x = 0 and x = \pm sqrt((k+(1/2))pi) for k = 0,1,2....

How do you get that answer?? I can see how the answer is x = 0, but how do you figure out the other one?
When is cos(x^2)=0?

3. Originally Posted by alexmahone
When is cos(x^2)=0?
for all integers?

4. Originally Posted by brumby_3
for all integers?
No.

cos(x^2)=0 when x^2=(k+(1/2))pi for k = 0,1,2....

So, x=?

5. is it sqrt[(k+(1/2))pi]

6. Originally Posted by brumby_3
is it sqrt[(k+(1/2))pi]
Don't forget the $\displaystyle \pm$.