Do you still need the answer, because im working on the same question..
Answer:
137473735858884506343
Step-by-step explanation:
Answer:
If it's not too late by now, the answer is 19.9 
Well, you would find the perimeter adding up all of the sides. Would you please tell us what each of the sides are, or what sides are what? :)
From my notes I’ve the derivative of arctan(x)= 1/(1+x^2)