The arms of a compass are each 12.5 cm long and their ends are 6.5 cm apart. Find the angle
between them.
how would this be set up? in a circle? Which side is the hypotenuse?

Question

The arms of a compass are each 12.5 cm long and their ends are 6.5 cm apart.  Find the angle 
      between them.
how would this be set up? in a circle? Which side is the hypotenuse?

whpalmer4 · Answer

Draw a picture:|dw:1391703928286:dw|

Note that $a$ in this drawing is half of the angle between them.

whpalmer4 · Answer

You should be able to find the value of $a$ from the definition of the $\sin$ function in a right triangle.