$\"\"$

The expression is $\"\"$ .

Find partial fraction of sum of power series of the expression.

General form of sum of power series for sine: $\"\"$

Let $\"\"$ .

$\"\"$ .

General form of sum of power series for cosine: $\"\"$

Let $\"\"$ .

$\"\"$ .

Therefore,

$\"\"$

Substitute above values in the expression.

$\"\"$

$\"\"$ .

Therefore the approximate value of the expression is $\"\"$ . $\"\"$

$\"\"$ .