Question

Find the principal value of $sec^{-1}(-1)$

Answer 1

Trigonometry is that branch of mathematics which deals with the relationship between the angles and sides of triangles. Inverse trigonometric function plays an important role in calculus and integrals.
Like: For Sine function: R—-->[-1,1],
For Cosec function : R—-->-(-1,1),
Therefore, $sec^{-1}(1)= 0$