If [tex]\sin (x+y)=\frac{\sqrt{3}}{2} \sin x+\frac{1}{2} \cos x[/tex], what is the value of [tex]y[/tex]?

A. [tex]\frac{\pi}{2}[/tex]
B. [tex]\frac{\pi}{3}[/tex]
C. [tex]\frac{\pi}{4}[/tex]
D. [tex]\frac{\pi}{6}[/tex]



Answer :

To determine the value of [tex]\( y \)[/tex] for the given equation

[tex]\[ \sin(x + y) = \frac{\sqrt{3}}{2} \sin(x) + \frac{1}{2} \cos(x), \][/tex]

we can use the identity for the sine of a sum of two angles. Let us compare the given equation to a known angle identity.

The sum of angles formula for sine is:

[tex]\[ \sin(A + B) = \sin(A) \cos(B) + \cos(A) \sin(B). \][/tex]

We want our given equation to match this form. Notice that:

[tex]\[ \sin(x + y) = \sin(x) \cos(y) + \cos(x) \sin(y), \][/tex]

The given equation is:

[tex]\[ \sin(x + y) = \frac{\sqrt{3}}{2} \sin(x) + \frac{1}{2} \cos(x). \][/tex]

By comparing the two forms, we see:

1. [tex]\(\sin(x + y)\)[/tex] corresponds to [tex]\(\sin(x) \cos(y) + \cos(x) \sin(y)\)[/tex].
2. [tex]\(\frac{\sqrt{3}}{2} \sin(x)\)[/tex] corresponds to [tex]\(\cos(y) \sin(x)\)[/tex].
3. [tex]\(\frac{1}{2} \cos(x)\)[/tex] corresponds to [tex]\(\cos(x) \sin(y)\)[/tex].

Let us focus on these individual components. The coefficient of [tex]\(\sin(x)\)[/tex] in the given equation is [tex]\(\frac{\sqrt{3}}{2}\)[/tex], which implies:

[tex]\[ \cos(y) = \frac{\sqrt{3}}{2}. \][/tex]

Similarly, the coefficient of [tex]\(\cos(x)\)[/tex] in the given equation is [tex]\(\frac{1}{2}\)[/tex], which implies:

[tex]\[ \sin(y) = \frac{1}{2}. \][/tex]

We need to find [tex]\( y \)[/tex] such that both [tex]\(\cos(y) = \frac{\sqrt{3}}{2}\)[/tex] and [tex]\(\sin(y) = \frac{1}{2}\)[/tex]. These are known values where:

[tex]\[ y = \frac{\pi}{3}. \][/tex]

Thus, the value of [tex]\( y \)[/tex] that satisfies the given equation is:

[tex]\[ \boxed{\frac{\pi}{3}}. \][/tex]