The trigonometric equation is in the interval .

and lies in second quadrant.

The point is on the circle of radius .

From Pythagorean theorem,

Since lies in second quadrant, is positive.

.

(a)

Find .

Use Double-angle formula: .

.

Substitute and .

.

(b)

Find .

Use Double-angle formula: .

.

Substitute and .

.

(c)

Find .

Use Half-angle formula: .

Substitute .

As , .

Where lies in first quadrant.

Therefore, is positive.

.

(d)

Find .

Use Half-angle formula: .

Substitute .

.

As , .

Where lies in first quadrant.

Therefore, is positive.

.

(a) .

(b) .

(c) .

(d) .