13. in the above figure, ∠aob = 80°. what does ∠acb equal? a. 10° b. 80° c. 40° d. 160°

take the logarithm of both sides (the base of the log doesn't matter):

apply the exponent property - this says that :

distribute the log terms on both sides:

group like terms together:

divide through both sides by the coefficient on :

you can do some additional rewriting here using the properties of the logarithm to simplify things if you like: