In some special cases where we add or subtract formulas for sine and cos, we get what is called as double-angle identities and half- angle identities. These half angle formulas let the trigonometric functions expressions of angles equate to x/2 in terms of x which can be later to functions and it would be easier to perform the complex calculations.
|Sin x/2 = ±√(1-cosx)/2|
Practice questions on Sin x/2 Formula
Question: Find the value of sin 105 degrees using Sin half-angle formulas
= √[(1 – (-√3/2)) / 2]
= √(2 + √3) /√ 4
= √ (2 + √3) / 2
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