Rút gọn biểu thức:

a) 1/tana + 1 + 1/cota + 1

`a)1/(tan a+1)+1/(cot a+1)`

`=(cot a +1)/((tana+1)(cot a+1))+(tan a+1)/((tan a+1)(cot a+1))`

`=(cot a+1+tan a+1)/((tan a+1)(cot a+1))=(cot a+tan a+2)/(tan a cot a+tan a+cot a+1)`

`=(cot a+tan a+2)/(1+tan a+cot a+1)`

`=(cot a+tan a+2)/(tan a+cot a+2)=1`