6. The Law of Sines and Law of Cosines
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Let's begin by drawing △DEF and labeling the lengths of the sides. We will also color code the opposite angles and sides. It will help us use the Law of Sines and Law of Cosines later.
Substitute values
Calculate power
Multiply
Add terms
LHS−656=RHS−656
LHS/(-640)=RHS/(-640)
-b-a=ba
Calculate quotient
Rearrange equation
Substitute values
With all of the angle measures, we can complete our diagram.