$\"\"$

\

(a)

\

The expression is $\"\"$ .

\

Let $\"\"$ , then $\"\"$ .

\

Trigonometric ratio : $\"\"$ .

\

$\"\"$ .

\

$\"\"$ .

\

Trigonometric ratio : $\"\"$ .

\

Pythagorean theorem : $\"\"$ .

\

$\"\"$

\

Trigonometric function : $\"\"$ .

\

Substitute $\"\"$ in $\"\"$ .

\

$\"\"$ .

\

$\"\"$

\

(b)

\

The expression is $\"\"$ .

\

Let $\"\"$ , then $\"\"$ .

\

Trigonometric ratio : $\"\"$ .

\

Pythagorean theorem : $\"\"$ .

\

$\"\"$

\

$\"\"$ .

\

Trigonometric ratio : $\"\"$ .

\

$\"\"$ .

\

Substitute $\"\"$ in $\"\"$ .

\

$\"\"$ .

\

$\"\"$

\

(a) The value of $\"\"$ is $\"\"$ .

\

(b) The value of $\"\"$ is $\"\"$ .