Спростіть вираз:
1) $1-\sin^2\alpha;$
2) $(1-\cos\alpha)(1+\cos\alpha);$
3) $\sin\left({90}^\circ-\alpha\right)+\cos\left({180}^\circ-\alpha\right);$
4) $\frac{\cos\left({90}^\circ-\alpha\right)}{\sin\left({180}^\circ-\alpha\right)}.$
1) $1-\sin^2\alpha;$
2) $(1-\cos\alpha)(1+\cos\alpha);$
3) $\sin\left({90}^\circ-\alpha\right)+\cos\left({180}^\circ-\alpha\right);$
4) $\frac{\cos\left({90}^\circ-\alpha\right)}{\sin\left({180}^\circ-\alpha\right)}.$