Help me b1 ạaaaaaaaa

`a)` `(2sin30^o - cos120^o)/(tan^2 60^o - cot 150^o)`

`=(2sin30^o + cos60^o)/(tan^2 60^o + cot30^o)`

`=(2sin30^o + sin30^o)/(tan^2 60^o + tan60^o)`

`=(3sin30^o)/(tan^2 60^o + tan60^o)`

`=(3/2)/(3 + sqrt3)`

`=(3-sqrt3)/4`

`b)`

`sin^2 22^o + sin^2 68^o + sin^2 31^o + sin^2 59^o`

`=sin^2 22^o + cos^2 22^o + sin^2 31^o + cos^2 31^o`

`=1+1`

`=2`

`c)`

`sin^2 54^o + sin^2 36^o - 3sin^2 126^o + cos^3 126^o + cos^3 54^o - 3cos^2 54^o`

`=sin^2 54^o + cos^2 54 - 3sin^2 126^o - 3cos^2 126^o + cos^3 126^o - cos^3 126^o`

`=1-3`

`=-2`

`d)`

`tan 5^o*tan10^o * tan15^o ... tan80^o * tan85^o`

`=tan5^o*cot5^o*tan10^o*cot80^o...*tan45^o`

`=1*1...1`

`=1`

`e)`

`cos0^o + cos20^o + cos40^o + ... + cos160^o + cos180^o`

`=cos0^o - cos0^o + cos20^o - cos20^o + ... + cos80^o - cos^80`

`=0 + 0 + ... + 0`

`=0`