1、\(\cfrac{3-sin70^{\circ}}{2-cos^210^{\circ}}=2\)
2、\(4cos50^{\circ}-tan40^{\circ}=\sqrt{3}\)
3、\(\cfrac{sin8^{\circ}+sin7^{\circ}cos15^{\circ}}{cos8^{\circ}-sin7^{\circ}sin15^{\circ}}=tan15^{\circ}=3-\sqrt{3}\)
4、\(cos\cfrac{\pi}{17}\cdot cos\cfrac{2\pi}{17}\cdot cos\cfrac{4\pi}{17}\cdot cos\cfrac{8\pi}{17}=\cfrac{1}{16}\)
5、\(sinx+cosx=\cfrac{\sqrt{2}}{2}\)，则\(sin^4x+cos^4x=\cfrac{7}{8}\)
6、\(\sqrt{1-2sin(\pi+2)cos(\pi+2)}=sin2-cos2\)
7、\(\sqrt{(1-tanx)^2+(1+tanx)^2}=-\cfrac{\sqrt{2}}{cosx}\)
8、\(\sqrt{(1-sin\alpha sin\beta)^2-cos^2\alpha cos^2\beta}=-2sin\cfrac{\alpha-\beta}{2}cos\cfrac{\alpha+\beta}{2}\)
