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