Solve your half of 1 4 problem step by step! We will develop formulas for the sine, cosine and tangent of a half angle.
Half Angle Formula – Sine We start with the formula for the cosine of a double angle that we met in the last section. As before, the sign we need depends on the quadrant. Next line is the result of multiplying top and bottom by `sqrt 2`. Next is a difference of 2 squares.
Of course, we would need to make allowance for positive and negative signs, depending on the quadrant in question. Next, we use the difference of 2 squares. Finally, we cancel out the sin α. Exercises: Evaluating and Proving Half-Angle Identities 1.