
William W. answered 10/12/21
Experienced Tutor and Retired Engineer
Subtraction of logs is the same as dividing the numbers inside the log so:
ln|cos(a)| - ln|cot(a)| is the same as ln|cos(a)/cot(a)| and since cot(a) = cos(a)/sin(a) we can say ln|cos(a)| - ln|cot(a)| is the same as ln|cos(a)/(cos(a)/sin(a)|
Then, simplifying what's inside: