Find the Sum of Cosine series when angle are in AP

Find the Sum of sine series when angle are in AP

If first term is 8 and last term is 20 common difffence is 2. find the value of n when the series are in AP.

In a convex polygon the interior angles are in AP, the smallest angle being 120^circ and the common difference 2^circ . Find the sum of the sines of the interior angles of the polygon if sin 1^circ = lambda ..

Problem on Trigonometric Series in Which angle are in A.P.

Problem on Trigonometric Series in Which angle are in A.P.

Find the sum of the series 2+6+18++4374

Find the sum of the series sum_(r=1)^(n)r xx r!

Find the sum of the series 1+4+10+22+...

Find the sum of the series: 5+13+21++181

The sum of the third and the seventh terms of an A.P. is 32 and their product is 220. Find the sum of the first twenty one terms of the A.P. (The terms of the A.P are in ascending order)