Упростить выражение: 1) [latex] \frac{1}{cos^2a} -tg^2a-sin^2a [/latex] 2) [latex] \frac{1}{cos^2a} -tg^2a(cos^2a+1) [/latex] 3) [latex] \frac{sina}{1+cosa} + \frac{sina}{1-cosa} [/latex]

1) [latex] \frac{1}{Cos^{2} \alpha } - \frac{Sin^{2} \alpha}{Cos^{2} \alpha}- \frac{Sin^{2} \alpha*Cos^{2} \alpha }{Cos^{2} \alpha }= \frac{Cos^{2} \alpha(1-Sin^{2} \alpha ) }{Cos^{2} \alpha} =Cos^{2} \alpha [/latex] 2) [latex] \frac{1-Sin^{2} \alpha*Cos^{2} \alpha -Sin^{2} \alpha}{Cos^{2} \alpha} =\frac{Cos^{2} \alpha(1-Sin^{2} \alpha ) }{Cos^{2} \alpha}=Cos^{2} \alpha [/latex] 3) [latex] \frac{Sin \alpha -Sin \alpha *Cos \alpha+Sin \alpha +Sin \alpha *Cos \alpha }{1-Cos^{2} \alpha } = \frac{2Sin \alpha }{Sin^{2} \alpha } = \frac{2}{Sin \alpha } [/latex]