0.52 divided by 0.0013

For the rule of 78, for a 12-month period, the last term in the sequence is 12 and the series sums to 78. for an 10 month period, the last term is and the series sum is . for a 15 month period, the last term is and the series sum is . for a 20 month period, the last term is and the series sum is

Need on this one asap im almost done with this subject

Solve for x where 0 equation: cot^2x+2cotx+1=0