Instantaneous velocity :the derivate of the displacement function
vx = 5t
vy = 15t²
at t = 0.25 s
vx = 1.25
vy = 0.9375
magnitude
[tex]\tt v=\sqrt{v_x^2+v_y^2}=\sqrt{1.25^2+0.9375^2}=1.5625~m/s[/tex]
direction
[tex]\tt \theta=tan^{-1}\dfrac{0.9375}{1.25}=36.87^o[/tex]