inverse trigonometric functions

• How to Calculate Inverse Trig Functions Without a Calculator
  Use principal ranges, exact unit-circle values, identities, and power series to evaluate inverse sine, cosine, and tangent by hand.
• How to Calculate Arcsine Without a Calculator
  Find exact inverse-sine values from special angles, or approximate arcsin(x) by a convergent power series with a practical error bound.
• How to Find the Inverse Cosine Without a Calculator
  Find an inverse cosine by recognizing unit-circle values, using symmetry, or converting arccos to an arctangent and evaluating its series by hand.