$\"\"$

(a)

The expression is $\"\"$ .

Apply formula: $\"\"$

$\"\"$

Substitute the values : $\"\"$

$\"\"$

$\"\"$ (Simplify)

$\"\"$ .

$\"\"$

(b)

The expression is $\"\"$ .

Substitute the values : $\"\"$ \ \

$\"\"$ \ \

$\"\"$ (Simplify)

$\"\"$ ( $\"\"$ ) $\"\"$

(a) The exact value of the expression is - 0.9659.

(b) The exact value of the expression is 1.2071.