# `a = 55, b = 25, c = 72` Use the Law of Cosines to solve the triangle. Round your answers to two decimal places.

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mathace | Certified Educator

Given: `a=55, b=25, c=72`

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` cos(C)=[a^2+b^2-c^2]/(2ab)`

` `

`cos(C)=[55^2+25^2-72^2]/(2*55*25)`

`cos(C)=-.5578`

`C=arccos(-.5578)`

`C=123.91^@`

`cos(A)=[b^2+c^2-a^2]/(2bc)`

`cos(A)=[25^2+72^2-55^2]/(2*25*72)`

` ` `cos(A)=.7733`

`A=39.35^@`

`B=180-123.91-39.35`

`B=16.74^@`