It looks like you're working with a trigonometric function. To clarify the expression you've presented:
If \( \sin(a_0) = \frac{1}{n} \), where \( n \) is a constant (and \( n \) must be greater than or equal to 1 for the sine function to be defined in this context, because the sine of an angle can only range between -1 and 1), then you can find \( a_0 \) as follows:
To find \( a_0 \), you'll take the inverse sine (arcsine) of both sides:
\[ a_0 = \arcsin\left(\frac{1}{n}\right) \]
This gives you the principal value of \( a_0 \). Keep in mind that the sine function is periodic, so general solutions for \( a_0 \) will include:
\[ a_0 = \arcsin\left(\frac{1}{n}\right) + 2k\pi \quad \text{and} \quad a_0 = \pi - \arcsin\left(\frac{1}{n}\right) + 2k\pi \]
where \( k \) is any integer.
If you have any specific questions about this or need further assistance, feel free to ask!