*Question:* find the equation of yacosxa that passes through the coordinates...

###### Question details

Find the equation of y=Acos(x/a) that passes through the coordinates (-4,2), and the vertex of (0,5)

Find the effect of the change in the parameter 'a' in the above equation

^find the effect in terms of vertex, dilation, and the amount of intersections with y^2 + x^2 = 25

Find the value 'a' such that the graph y= Acos(x/a) has more than 1 point of intersection with y^2 + x^2 = 25 but no more than one intersection with y^2 + x^2 = 16

please show full working out and please make the answer as detailed as possible. i would really appreciate a response as soon as possible :)