Find an equation of a plane making an angle of pi/2 with the plane 3x+y-4z=2

The formula for getting the equation of a plane making an angle of pi/2 with the plane 3x + y - 4z = 2 is

π/2 = cos⁻¹ |3a + b - 4c | / [√ (3² + 1² + (-4) ²) + √ (a² + b² + c²) ]

Try assuming values for the variables and solve the other variable.