Circle J has center J(4, -3) and radius 5. What is the measure, in degrees, of the arc with the endpoints A(9, -3) and B(4,2)?

Question

Circle J has center J(4, -3) and radius 5.  What is the measure, in degrees, of the arc with the endpoints A(9, -3) and B(4,2)?

phi · Answer

do you know about vectors  ?
if so I would find V=  A-J  and W= B-J
we get  V= (9,-3) - (4,-3) =  (5,0)
and W= (4,2) - (4, -3) =  (0,5)

we can think of this as translating (sliding) the circle so its center is at (0,0)

in other words, we get this picture
|dw:1431608541184:dw|
you can see the angle must be 90 degrees