I'm guessing the sum is supposed to be

Split the summand into partial fractions:


If
, then

If
, then

This means

Consider the
th partial sum of the series:

The sum telescopes so that

and as
, the second term vanishes and leaves us with

4.2 is the answer of this question you are asking ✌️
U can easily put this through a calculator, but it’s 24 :)
Answer:
There are 7 sides.
Step-by-step explanation:
Let's Use the formula that states that the sum of the angles of an n-sided polygon is given by.
S=(n−2)180
Since we are given that the two angles are right, the angles and each of the remaining angles is 144.
And Therefore, the sum is:
S=90
(n−2)144
(n−2)180
=90
+90
+(n−2)144
⇒(n−2)180
−(n−2)144
=180
⇒(n−2)(180
−144
)=180
⇒(n−2)(36
=180
⇒n−2=
36
180
⇒n−2=5
⇒n=5+2=7
Hence, the polygon has 7 sides.