 
 
 Draw a right triangle with angle x, hypotenuse 1, and legs "a" and "b"
Draw a right triangle with angle x, hypotenuse 1, and legs "a" and "b"
 
 
 Since
Since  , that's
because by the Pythagorean theorem, a2+b2=1
, that's
because by the Pythagorean theorem, a2+b2=1
 Multiply top and bottom by a2b2
Multiply top and bottom by a2b2
 We multiply out the denominator,
We multiply out the denominator,
 Since a2+b2=1,
Since a2+b2=1,
 
 The denominator factors
The denominator factors
 Multiply by the product of the "conjugates" of the
factors on the bottom over itself. (Sort of like
rationalizing the denominator)
Multiply by the product of the "conjugates" of the
factors on the bottom over itself. (Sort of like
rationalizing the denominator)


 
 
 By the Pythagorean theorem  1-a2=b2 and 1-b2=a2
By the Pythagorean theorem  1-a2=b2 and 1-b2=a2
 Canceling:
Canceling:
 Since a = sin(x) and b = cos(x)
Since a = sin(x) and b = cos(x)
 <--simplest form
Edwin
  <--simplest form
Edwin