# Trigonometry Trigonometry helps you understand any topic that involves distances, angles, or waves. The trig functions (sin, cos, and tan) show up all over science and engineering.

« Back to dashboard What's a "radian"? Discover another way to measure angles. Radians and degrees How to switch back and forth between units for angles Lengths of circular arcs A formula for arc length in terms of radius and angle Sectors Learn what a sector is, and a formula for finding its area
2. Trig functions Sides of right triangles  Sine  Cosine Along with sine, cosine is a fundamental trig function Tangent Another important trig function (like sine and cosine) Components (and cops) Find legs of right triangles, and don't get pulled over! Sec, Csc, and Cot Secant and friends (three more trig functions)
3. Special angles 45 degrees Calculate the sine, cosine, and tangent of 45 degrees 30/60 degrees Calculate the sine, cosine, and tangent of 30 and 60 degrees 0/90 degrees Calculate the sine, cosine, and tangent of 0 and 90 degrees
4. The unit circle Trig for larger angles What's sin(250)? Use the unit circle to tackle bigger angles Trig for negative angles Using the unit circle for trig with negative angles Trig for coterminals How trig functions are related for coterminal angles
5. Inverse trig functions Inverse sine A function that takes you from side ratios to angles Inverse cosine Another inverse trig function Inverse tangent And one last inverse trig function!
6. Trig identities Trig identities The tools for simplifying trig expressions Addition identities Simplify trig functions of sums Negative angle identities Simplify trig functions of negative angles Subtraction identities Simplify trig functions of differences Double angle identities Trig functions of twice an angle Triple angle identities Trig functions of three times an angle Pythagorean identities Relating squares of trig functions Half angle identities Trig functions of half an angle
7. Triangle formulas Law of sines Relating angles and opposite sides for any triangle Triangulation Real-world application of the law of sines to find distances Law of cosines Relating three sides and an angle for any triangle Triangle area: SAS Find a triangle's area using 2 sides and the angle between