The trigonometric expression is
.
, let
and place
in quadrant III.
The point P = (x, y) = (12, 5) is on a circle of radius,
.
(Substitute
)
(Simplify)
(Simplify)
(Simplify)
(Substitute y = 5, r = 13)
(Substitute x = 12, r = 13)
, let
and place
in quadrant III.
The point P = (x, y) =
= x < 0 is on a circle of radius,
.
(Substitute
)
(Simplify)
(Subtract 1 from each side)
(Simplify)
(x < 0)
(Substitute
, r = 2)
a) 
The sum formula for the sine function:
.
Substitute
.

(Simplify)
(Rewrite the expression with common denominator)
The value of 
.