Under the rotation of axes through an angle 15° in anti clock wise sense the equation $3\mathrm{x}+4\mathrm{y}+15=0$change to $\mathrm{aX}+\mathrm{bY}+\mathrm{c}=0\text{ then }\frac{\left|\mathrm{c}\right|}{\sqrt{{\mathrm{a}}^2+{\mathrm{b}}^2}}=$