The given in the triangle are `A=120^o` , `b=6` and `c=7` . To solve for the values of a, B and C, let's apply Cosine Law.
For side a:
`a^2=b^2+c^2-2*b*c*cosA`
`a^2=6^2+7^2-2*6*7cos(120^o)`
`a^2=36+49-84cos(120^o)`
`a^2=127`
`a=sqrt127`
`a=11.27`
For angle B:
`b^2=a^2+c^2-2*a*c*cosB`
`6^2=(sqrt127)^2+7^2-2*sqrt127*7*cosB`
`36=176-14sqrt127cosB`
`(36-176)/(-14sqrt127)=cosB`
`cos^(-1)((36-176)/(-14sqrt127))=B`
`27.46^o=B`
For angle C:
`c^2=a^2+b^2-2*a*b*cosC`
`7^2=(sqrt127)^2+6^2-2*sqrt127*6*cosC`
`49=127+36-12sqrt127cosC`
`49=163-12sqrt127cosC`
`(49-163)/(-12sqrt127)=cosC`
`cos^(-1)((49-163)/(-12sqrt127)=C`
`32.54^o=C`
Thus, the sides of the triangles are:
`a=11.27`
`b=6`
`c=7`
And its angles are:
`A=120^o`
`B=27.46^o`
`C=32.54^o`
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