Question: I am trying to round the corners of a custom shape, but it is just straightening the original curves out.

*Note: This is in Illustrator CS5*

**Here is the shape before the effect:**

[![enter image description here](https://i.stack.imgur.com/luohd.png)](https://i.stack.imgur.com/luohd.png)

The 3 "corners should be rounded".

**Here is what happens when I use the effect:**

[![enter image description here](https://i.stack.imgur.com/3jyfQ.png)](https://i.stack.imgur.com/3jyfQ.png)

**How can I preserve the curves, and just round the actual corners?**

Answer: 
I don't have CS5, but this should work:

Select your path. With the pen tool selected, create points on each side of the anchor points, something like the following:

[![Path with new anchor points added near the original cusp points.](https://i.stack.imgur.com/U3Mk7.png)](https://i.stack.imgur.com/U3Mk7.png)

With the white arrow tool selected, click one of the original cusp points (i.e., corner points) and then `Shift`-click the other two to select all three. Then, click the `Convert selected anchor points to smooth` icon in the toolbar at the top of the screen (alternatively, with the pen tool selected you can `Alt` or `Option`-drag on a corner point to convert it to a smooth point):

[![Convert selected anchor points to smooth icon](https://i.stack.imgur.com/mchHs.png)](https://i.stack.imgur.com/mchHs.png)

You should end up with something similar to this:

[![Path with bulging corners.](https://i.stack.imgur.com/zOo3s.png)](https://i.stack.imgur.com/zOo3s.png)

With the white arrow tool, drag each of the bulging corner points inward until they look appropriate:

[![Bulging corner points fixed.](https://i.stack.imgur.com/glD9N.png)](https://i.stack.imgur.com/glD9N.png)

Here's the new path overlaying your original shape.

[![Path with rounded corners.](https://i.stack.imgur.com/Mz93L.png)](https://i.stack.imgur.com/Mz93L.png)

If you want the corners to be more rounded, make sure the anchor points you added in the first step are farther away from the corner points.
My way is easier if you have good experience with the pen tool.

First, make your triangle. In my case, I just made a box, deleted 1 anchor point, joined the two points creating a segment opposite to the middle point and rotated about 45 degrees (please correct me if I'm wrong). 

[![enter image description here](https://i.stack.imgur.com/sXe3V.png)](https://i.stack.imgur.com/sXe3V.png)

Next, hit the convert path to rounded corner button. I'm pretty sure this feature is already in CS5. Make sure you have the point selected when doing this.

[![enter image description here](https://i.stack.imgur.com/ZjWmA.png)](https://i.stack.imgur.com/ZjWmA.png)

Do this one by one for each of your points. The one in the middle should be the easiest one to convert. The one at the top and the bottom are a bit tricky but nothing a pen tool can't fix :)

As you go each of the top and the bottom points, with your Direct Selection Tool active, grab the furthest to the left angle for the point being selected and while holding Shift, bring it to the center creating a nice straight side but still rounded corners. 

[![enter image description here](https://i.stack.imgur.com/Z6DvZ.png)](https://i.stack.imgur.com/Z6DvZ.png)

It should look something like this:

[![enter image description here](https://i.stack.imgur.com/Jj8Te.png)](https://i.stack.imgur.com/Jj8Te.png)

Again, do the same thing for the bottom and you will get this:

[![enter image description here](https://i.stack.imgur.com/WQiBV.png)](https://i.stack.imgur.com/WQiBV.png)

I hope this helps! Please let me know if I confuse you. I'll be glad to clarify myself some more.