Latika Leekha
Last Activity: 10 Years ago
Let us assume tan-1(-1) = y.
Then we have tan y = -1
This can be written as tan y = tan (-

/4)
Also, we know that the range of principal value branch of tan
-1y is (-

/2,

/2),
hence, this means that y = -

/4.
Hence, the principal value of tan
-1(-1) is -

/4.
Thanks & Regards
Latika Leekha
askIITians Faculty