$$I=\sqrt{\left(\frac{I_{m1}}{\sqrt{2}}\right)^2+\left(\frac{I_{m2}}{\sqrt{2}}\right)^2+\left(\frac{I_{m3}}{\sqrt{2}}\right)^2+\cdots +\left(\frac{I_{mn}}{\sqrt{2}}\right)^2} \tag{1.90}$$
$$I=\sqrt{\left(\frac{I_{m1}}{\sqrt{2}}\right)^2+\left(\frac{I_{m2}}{\sqrt{2}}\right)^2+\left(\frac{I_{m3}}{\sqrt{2}}\right)^2+\cdots +\left(\frac{I_{mn}}{\sqrt{2}}\right)^2} \tag{1.90}$$