Perfect Edges

How would you go from A to B to get the perfect edges?

Open up a new document.

Open a new layer. Using any medium you like, trace a shape. Here I used a hard Brush to somewhat make a triangle.

Press Ctrl and left click on your shape layer. Your shape should now be selected.

Now enter Quick Mask by pushing Q on your keyboard.

Go to Filter > Blur > Gaussian Blur and enter in the settings above.

Next go Image > Adjustments > Brightness/Contrast. In Contrast enter 94.
Now drag the Brightness slider to the Left until you are satisfied with the edges. You should see the edges start to smoothen out.

Press Q again to exit Quick Mask mode. You should have a selection slightly bigger than your original.
Make a new layer and, selecting the Fill tool, fill the selection with your desired colour.
You should now have a nearly perfect triangle!