Revered members, i have attached two images which depicts obtaining an expression for velocity and acceleration of particle executing SHM.
In the first attachment, velocity component vcos[itex]\Theta[/itex] is parallel to vertical diameter of the circle and vsin[itex]\Theta[/itex] is perpendicular to the vertical diameter.
In the second attachment, acceleration component vcos[itex]\Theta[/itex] is perpendicular to vertical diameter and vsin[itex]\Theta[/itex] is parallel to vertical diameter.
The Attempt at a Solution
I know perpendicular component is sine and parallel component is cosine. But i can't understand why perpendicular component to vertical diameter is taken as cosine in acceleration expression and parallel component as sine? Please help revered members, with regard to guidelines for resolving vectors in cosine and sine components.