The axis of symmetry of a parabola like

is a vertical line of the form

where k is the x coordinate of the vertex of the parabola.
In particular, the x coordinate of the vertex of the parabola is given by

which in your case becomes

So, the axis of symmetry is the line

<span>The correct answer is A. X=5, Y=6. Both triangles are right triangles. Each triangle has corresponding sides that are congruent which makes the triangles congruent. The answer A has the values that make each side of both triangles equal to the other triangle.</span>
The maximum value is actually the maximum of y
So, you don't need to care about the stuff inside cosine function,
Cosine function is always within the range of [-1,1]
So here, ymax = -1 + 6* 1 = 5