# Trigonometry

By Levi Clancy for Student Reader on *updated *

sin | sin θ = cos ( θ - ½ π ) |
---|---|

cos | cos θ = sin ( θ + ½ π ) |

###### Small Angle Approximations

When θ is extremely small, for example if one cathetus is several orders of magnitude than the other, we can use the following approximations:

sin θ ≈ θ

cos θ ≈ 1 - ½ θ^{2}tan θ ≈ θ