Use the appropriate formula for the given shape or situation
For a right triangle, use trigonometric ratios: sin θ = opposite/hypotenuse, cos θ = adjacent/hypotenuse, tan θ = opposite/adjacent
Rearrange the ratio to isolate θ using inverse trig functions
Calculate θ with sin⁻¹, cos⁻¹, or tan⁻¹ on a calculator
For a circle, use θ = arc length/radius when angle is in radians
For a sector, use θ = 2A/r² when area and radius are known
For a line on a coordinate plane, use θ = tan⁻¹(slope)
For vectors, use cos θ = (a·b)/(|a||b|)
For polygons or geometry problems, use angle sum rules, supplementary angles, or complementary angles
Substitute the known values into the correct equation
Solve for θ
Check whether the answer should be in degrees or radians