Question

f(x)=cot(x)-cot^2(x)+cot^3(x)-....upto infinity and if a+b=5π/4. Find f(a)+f(b).

Answer 1

Hey i can tell you the approach hope you can easily solve it..
# Take cotx common from the function and you will get a G.P. Solve its summation upto infinity by using formula a/1-r .
#You will get cotx/1-cotx convert it into sin-cos form as it will be easier for you to solve.
#Now put the values of a and b in the obtained function.
#Solve it and on solving you will fin a+b in you r function on putting the value(given) you will get the answer.