cot7(1^(@))/(2)" is equal to "

cot^(-1)(-2) is equal to

cot^(-1)(-2) is equal to

Value of the expression (sec1 1^(@)sec1 9^(@)-2cot7 1^(@))/tan11^(@) is equal to

Value of the expression (sec1 1^(@)sec1 9^(@)-2cot7 1^(@))/tan11^(@) is equal to

If the mapping f(x)=ax+b, a>0 maps [-1,1] on to [0,2] then cot[cot^(-1)(7)+cot^(-1)(8)+cot^(-1)(18)] is equal to

cot^(-1)(-1/2)+cot^(-1)(-1/3) is equal to

cot^(-1)(-1/2)+cot^(-1)(-1/3) is equal to