Answer:
![(x)/(√(x^2+9))](https://img.qammunity.org/2021/formulas/mathematics/high-school/jmug5a2wnjhgqrqeqfdln9oudb2whwt0un.png)
Explanation:
Let
.
Then
.
Construct a right triangle.
Make one of the non-right angles
.
Recall
is equal to the ratio of the side that is opposite to
to the side that is adjacent to
.
This means opposite side
while adjacent side
since
.
We can find the hypotenuse by using the Pythagorean Theorem.
![(x)^2+(3)^2=(\text{hyp})^2](https://img.qammunity.org/2021/formulas/mathematics/high-school/5rrpapgzxwwmnop6mfx5uwq3w4x84eqbw6.png)
![x^2+9=(\text{hyp})^2](https://img.qammunity.org/2021/formulas/mathematics/high-school/rk8p33zx70albygry45lqni6ar1jb71c04.png)
Take the square root of both sides:
.
Recall
is equal to the ratio of the side that is opposite to
to the hypotenuse.
![\sin(\arctan((x)/(3)))](https://img.qammunity.org/2021/formulas/mathematics/high-school/ysr9dv26z7livzvvbgrd6ky6uhzhwqgxq3.png)
-->Because we let the inside equal
.
-->Because
![\sin(u)=\frac{\text{opp}}{\text{hyp}}](https://img.qammunity.org/2021/formulas/mathematics/high-school/ak2edny794d8y1pivzswkbafvq3hqis17j.png)