How do you evaluate tan^-1(tan((19pi)/10))tan1(tan(19π10))?

1 Answer
Jul 21, 2016

(19/10)pi(1910)π.

Explanation:

tan^(-1)tan((19pi)/10)tan1tan(19π10) is

the angle whose tangent is tan ((19pi)/10)tan(19π10)

=(19/10)pi=(1910)π.

From the definitions of successive operations

f f^(-1) (y)=yff1(y)=y and

f^(-1)f(x)=x,f1f(x)=x,

only the operand value has to be given as the answer and

not any other value, from the general value

npi+(19pi)/10, n = 0, +-1, +-2, +-3....

Here, f = tan and f^(-1)=tan^(-1).