How do you define a radian

It is a unit of angle and is equal to an angle at the center of a circle. The arc will be equal in length to the radius. Hope this helped.

you didn't post any answer choices, so its not 100% clear what your teacher is looking for

however, log(15/7) is equivalent to log(15) - log(7)

i'm using the rule log(x/y) = log(x) - log(y)

can you complete your sentence? i could !