Sine and cosine rules and areas of any triangle

With reference to triangle ABC of Figure. 48.1, the sine rule states: Figure 48.1 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429294402/968186b9-ffa4-4f2b-aa54-7fc58a604561/content/fig48_1.tif"/> a sin A = b sin B = c sin C https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429294402/968186b9-ffa4-4f2b-aa54-7fc58a604561/content/eq1633.tif"/>