C. The Sine Law
Completion requirements
C. The Sine Law
In Section A and Section B, you have used either the primary trigonometric ratios or the cosine law to solve various triangles. Suppose you are asked to find the length of one side of a roof truss, given the following diagram.
First, notice that the triangle is oblique, but the cosine law does not work here because you are not given the correct combination of information.
If you tried to use the primary trigonometric ratios, you would draw an altitude from the peak to the base, and work with two right triangles.
However, this is still not useful because you do not have the length of one of the sides of either of the right triangles. The result is the need for another useful tool. In this lesson, you will discover and use this new tool – the sine law.
If you tried to use the primary trigonometric ratios, you would draw an altitude from the peak to the base, and work with two right triangles.
However, this is still not useful because you do not have the length of one of the sides of either of the right triangles. The result is the need for another useful tool. In this lesson, you will discover and use this new tool – the sine law.