Answer:
, 
Step-by-step explanation:
Given
the equation is 
completing the square

Thus, the center of the circle is
and radius is 
Answer:
3
Step-by-step explanation:
AC = √(40²-12²) = √(1600-144) = √1456 = 4√91
tanA = 12/4√91 = 3/√91 = 3√91/91
option а.
It would be: 311*84 / 100 = 311 * 0.84 = 261.24
So, your answer is 261.24