notes/education/math/MATH1060 (trig)/Law of Sines.md
2024-11-11 21:43:16 -07:00

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Intro

Tl;dr, the law of sines is:

 \frac{\sin(\alpha)}{a} = \frac{\sin(\beta)}{b} = \frac{\sin(\gamma)}{c} 

Under convention:

  • Angle \alpha is opposite side a

  • Angle \beta is opposite side b

  • Angle \gamma is opposite side c

  • Any triangle that is not a right triangle is called an oblique triangle. There are two types of oblique triangles:

    • Acute triangles: This is an oblique triangle where all three interior angles are less than 90\degree or \dfrac{\pi}{2} radians.
    • Obtuse Triangle: This is an oblique triangle where one of the interior angles is greater than 90\degree.

Different types of oblique triangles

  1. ASA Triangle: (Angle Side Angle) - We know the measurements of two angles and the side between them
  2. AAS: We know the measurements of two angles and a side that is not between the known angles.
  3. SSA: We know the measurements of two sides and an angle that is not between the known sides. These triangles can be solved by adding a line that goes from one vertex to intersect perpendicular to the opposite side, forming two right triangles (h).

Solving for the law of sines

We know that \sin\alpha = \dfrac{h}{b}