Step-by-step explanation:
½ [cos(a − b) − cos(a + b)]
Using sum and difference formulas:
½ [cos a cos b + sin a sin b − (cos a cos b − sin a sin b)]
Distribute the negative:
½ (cos a cos b + sin a sin b − cos a cos b + sin a sin b)
Combine like terms:
½ (2 sin a sin b)
Simplify:
sin a sin b
The equation of a circle:

(h, k) - a coordinates of the center
r - a radius

Answer:
the center: (3, -2)
the radius: 3
Answer:
v8
Step-by-step explanation:
what the other guy said!