$tan\,\, 20^o + tan\,\, 40^o + \sqrt 3\,\,  tan\,\, 20^o tan\,\, 40^o$ is equal to

Prove the $\cos \left(\frac{3 \pi}{2}+x\right) \cos (2 \pi+x)\left[\cot \left(\frac{3 \pi}{2}-x\right)+\cot (2 \pi+x)\right]=1$

Prove that $\frac{\cos (\pi+x) \cos (-x)}{\sin (\pi-x) \cos \left(\frac{\pi}{2}+x\right)}=\cot ^{2} x$

If $\sin \theta + {\rm{cosec}}\theta = 2,$ the value of ${\sin ^{10}}\theta + {\rm{cose}}{{\rm{c}}^{10}}\theta $ is

If $2y\,\cos \theta = x\sin \,\theta {\rm{ and }}2x\sec \theta - y\,{\rm{cosec}}\,\theta = 3,$ then ${x^2} + 4{y^2} = $

Prove that $2 \sin ^{2}\, \frac{3 \pi}{4}+2 \cos ^{2}\, \frac{\pi}{4}+2 \sec ^{2}\, \frac{\pi}{3}=10$