This is reply by AI

For finding the equation of tangent
y = mx+c
we need m and c

dx/dQ = 2_/2* QcosQ
dy/dQ = 2_/2* QsinQ
dy/dx at Q= pi/4 = 1

so y = x + c
In order to find c we need to put Q=pi/4 in both equations and then use the value of x and y in y= x+c

x = 2*(1 + pi/4)
y = 2*( 1- pi/4)
y = x+c
2 - pi/2 = 2+ pi/2 + c
c = -pi

y = x -pi
so pi = x-y