Trigo Sine Rule
In this lesson, you will learn how to apply the Sine Rule to solve triangles that are not right-angled. The Sine Rule helps you find missing sides or angles when have two sides, two angles, including the unknown side or angle. It works by equating the ratio of each side to the sine of its opposite angle to form a pair.
Related Lessons:
Sine Rule
When applying the Sine Rule, to simplify the algebraic manipulation, there are two forms you can use, depending on whether you are solving for an unknown side or an unknown angle.
For unknown angle, we will place the trigo as a numerator:
\(\frac{sin{A}}{a}=\frac{sin{B}}{b}=\frac{sin{C}}{c}\)
For unknown side, we will place the side as a numerator:
\(\frac{a}{sin{A}}=\frac{b}{sin{B}}=\frac{c}{sin{C}}\)
Example 1
In this first example, we are asked to calculate angle BAC.
Example 2
In this second example, we are required to calculate the length of AC.