Answer:
Center: (-5,10)
Radius: 2
Step-by-step explanation:
The equation of the circle in center-radius form is:
Where the point (h,k) is the center of the circle and "r" is the radius.
Subtract 121 from both sides of the equation:
Add 10x to both sides:
Make two groups for variable "x" and variable "y":
Complete the square:
Add 
inside the parentheses of "x".
Add 
inside the parentheses of "y".
Add 
and 
to the right side of the equation.
Then:
Rewriting, you get that the equation of the circle in center-radius form is:
You can observe that the radius of the circle is:
And the center is:
5x - 100 + x - 20 = 180 (sum of supplementary angles is equal 180)
6x - 120 = 180
6x = 300
x = 50
x - 20 = 50 - 20 = 30
so
3y = 30 (vertical angles are equal)
y = 10
We presume the temperature is decreasing at midnight, so reaches a low at 6 a.m.. The amplitude of the variation is (87-63)/2 = 12 degrees. We want the period to be 24 hours, so the argument of the sine function will be 2π(t/24) = πt/12. Then we can write
... d = 75-12sin(π·t/12)
114°+x°=180
Subtract 114° for both side
x=66°. Hope it help!
1 because it is reveresed
