Derivative of a trig. function

[frosty8688]

1. Find the derivative of the function using the power rule or product rule



2. sinθ/2 + c/θ



3. I tried to do plus or minus the √1-cosθ/2

 

[eumyang]

Your question is ambiguous. Please use parentheses. It looks like that want to find the derivative of
$$\frac{\sin \theta}{2} + \frac{c}{\theta}$$

 

[frosty8688]

Yes, that's it

 

[Saitama]

There is no need to plus or minus the √1-cosθ/2, simply find the derivative of sin θ and 1/θ w.r.t θ (I suppose that's what you are asked.) And what about c? How is it defined in the question?

 

[frosty8688]

Here's what I have (cosθ/2) + (c/θ). c is a variable.

 

[e^(i Pi)+1=0]

The c probably stands for some constant.

 

[frosty8688]

ok, thanks.

 

[eumyang]

Here's what I have (cosθ/2) + (c/θ). c is a variable.

If c is a constant, and the above is your solution attempt, then you have to do something with the 2nd term (ie. the derivative of c/θ isn't c/θ).

 

[frosty8688]

The solution would be (cosθ/2).

 

[Saitama]

The solution would be (cosθ/2).

No, how do you get this? What's the derivative of 1/θ?

 

[frosty8688]

The derivative of a constant is 0.

 

[eumyang]

The solution would be (cosθ/2).

Sorry, that's wrong. If the original problem was this:
$$\frac{\sin \theta}{2} + c$$
(with c as a constant), then your answer would be right. But the 2nd term has a θ in the denominator. What do we do?

 

[frosty8688]

It would be (cosθ/2 - c/θ^2)

 

[Saitama]

It would be (cosθ/2 - c/θ^2)

Looks good.