ALPHA } \right\}\] Þ \[{{(u-\sin \theta \cos \theta )}^{2}}={{\cos }^{2}}\theta ({{\sin }^{2}}\theta +{{\sin }^{2}}\alpha )\] Þ \[{{u}^{2}}{{\tan }^{2}}\theta -2u\tan \theta +{{u}^{2}}-{{\sin }^{2}}\alpha =0\] SINCE tan \[\theta \]is REAL, therefore Þ \[4{{u}^{2}}-4{{u}^{2}}({{u}^{2}}-{{\sin }^{2}}\alpha )\ge 0\] \[\Rightarrow {{u}^{2}}-(1+{{\sin }^{2}}\alpha )\le 0\] Þ \[|u|\,\le \sqrt{1+{{\sin }^{2}}\alpha }\].