__Sine
and Cosine Subtraction Formulas__

Now, we will try to prove the Sine and Cosine
Subtraction Formulas using the Figure 2 below.
ABCD is
a quadrilateral such that angle ABC and angle CDA are right angles
and angle DAB is acute. X denotes the angle DAB and Y denotes
the angle CAB. Thus angle CAD is X-Y.

**The
**__Sine
Subtraction Formula__ states that
**sin(x-y)
=sin(x)cos(y) - cos(x)sin(y).**

**Let's
see if we can prove this formula using the Figure 2 above!**
**Therefore,
we have proved the Sine Subtraction Formula does, in fact work**

**Now, let's try
proving the Cosine Subtraction Formula.**

The __Cosine Subtraction
Formula__
states that
**cos(x-y)
=cos(x)cos(y) + sin(x)sin(y).**

Now,
we have proved that the Cosine Subtraction Formula does work.
__RETURN__