Step 1:

(a)

The trigonometric function is , .

Since lies in quadrant I, then is also lies in quadrant I.

Step 2:

(b)

Find .

Using half - angles formulas : .

Substitute in above formula.

.

Find .

Using half - angles formulas : .

Substitute in above formula.

.

Find .

Using half - angles formulas : .

From Pythagorean theorem, .

Substitute and in above formula.

.

Solution :

(a) lies in quadrant I.

(b) , and .