Finding the Angle of a Dart.

The patternmaking software that I use does not have a utility to measure angles and yet it requires the angle measurement in order to rotate pieces on the screen(!).  I used to guess and use the undo button a lot until my husband gave me this simple formula to use.  You'll need a calculator that does trigonometric functions, the length of one leg of the dart to be closed (c) and the width of the dart (a).

Here's an example:

The dart leg length is 7.25"(c), the dart width is 1.0" (a).
Half the width is .5" (b)

.06897=.5/7.25
this is the sine of the angle.

To find the angle of this sine you'll need to get the inverse sine represented by sin-1 on your calculator.
3.954

Since we halved the dart width this number is only half of our angle:
angle of the dart = 7.908 = 2(3.954)

So if I'm transferring the side dart to the shoulder I can rotate my pattern pieces down by 7.908 degrees.  Remember to extend the dart to the bust point before pivoting.

If you're not used to using a calculator with trigonometric functions use the example above as a check.

questions?  email lindrix