What is the radius of the circle with this equation of (x-5)^2+(y+7)^2=8

i have no idea

You didn't give me an angle but here's how to us a protractor

Step-by-step explanation: To measure an acute angle (less than 90   degrees), put the vertex at  

the center of the straight side of the protractor, lining up one half  

of that side with one side of the angle, so that the other side is  

under the protractor. On the curved edge of the protractor are  

(usually) two sets of numbers; one scale starts with zero on the left  

edge and increases to the right, while the other starts with zero on  

the right edge and increases to the left. Choose the scale that starts  

on the side that you lined up with a side of the angle. Read off the  

number from this scale at the point where the other side of the angle  

crosses the protractor.