Calculate the acute angle between two intersecting surfaces whose equations are as follows:
$$2x - 4y - z = -5$$
$$3x + 4y + 5z = -6$$
What is the equation of the normal to the curve $x^2 + y^2 = 25$ at (4, 3)?
What is the radius of the circle $x^2 + y^2 - 6x = 0$?
Find the distance from the point A(1, 5, -3) to the plane 4x + y + 8z + 33 = 0.