Consider two circles C1: x2+y2=25 and C2:(x- )2+y2=16, where (5,9). Let the angle between the two radii (one to each circle) drawn from one of the intersection points of C1 and C2 be -1 ( 638 ). If the length of common chord of C1 and C2 is , then the value of ( )2 equals .
Answer
1575
Solution
[figure]
In ': OP=5, O'P=4, OO'= , = 638
∵ OO′ bisects the common chord PQ at right angles PM= 2
Area '= 12 5 4 = 12 2
=40 =40 638=5 63
( )2=25 63=1575
Answer: 1575