Page 37 - Ebook Trigonometri_Krisna Hasugian_MESP 2019

Law of Sines and Cosines

These laws help us to find missing information when dealing with oblique
triangles (triangles that are not right triangles)

Law of Sines

sin sin sin
= =

You can use the Law of Sines when the problem is referring to two sets of angles
and their opposite sides.

Example 38 Find the length of AB. Round your answer to the nearest tenth.

Since we are given information about an angle, the side opposite of
that angle, another angle, and missing the side opposite of that angle,
we can apply the Law of Sines.

sin 92° sin 28°
=
15

Multiply both sides by the common denominator in order to eliminate
the fractions. We do this so that we can solve for the unknown. This
gives us,

sin 92 ⋅ = sin 28 ⋅ 15

Then we can divide by sin 92. When we do this we find = 7

Law of Cosines

² = ² + ² − 2 cos

² = ² + ² − 2 cos

² = ² + ² − 2 cos

You can use the Law of Cosines when the problem is referring to all three sides

and only one angle.

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