Physics

The projection of a point onto the vertical diameter is just its $y$-coordinate, which equals $A\sin\theta$ for a circle of radius $A$. To find where this projection reaches its maximum positive value, you need to find where $\sin\theta$ is largest—this is a straightforward optimization problem. Think about the unit circle: the $y$-coordinate climbs as you move counterclockwise from the positive $x$-axis, peaks at the top, then descends.

The projection of a point onto the vertical diameter is just its $y$-coordinate, which equals $A\sin\theta$ for a circle of radius $A$. To find where this projection reaches its maximum positive value, you need to find where $\sin\theta$ is largest—this is a straightforward optimization problem. Think about the unit circle: the $y$-coordinate climbs as you move counterclockwise from the positive $x$-axis, peaks at the top, then descends.