Trigonometry

• How do you use the cosine rule to find a side?

  c² = a² + b² - 2ab cos(C)

  
• How do you use the cosine rule to find an angle?

  cos(C) = $\frac{a^2 + b^2 - c^2}{2ab}$

  
• Area of any triangle

  $\frac{1}{2}$$ab$$\sin$(C)