Ritika M.

# MATHS INVERSE TRIGNOMETRY PRINCIPAL VALUES

For finding the principal value,in this question:

Find the principal value of cot-1(-1/√3)

The answer is cot(π-π/3) which is cot (2π/3)

why is it not just -π/3?

In a similar question, Find the principal value of sin-1(-1/2), I tried doing sin(π+π/6) since sin is negative in 3rd quadrant.But the answer was just -(π/6).Why is there this difference?Someone please explain.Thank You