Respuesta :
To find the length of the third side of the triangle, the law of cosines is needed.
Let's say, for the sake of solving this problem the side with the length of 2 is a, that with the length of 5 is b, and the unknown is c. The known angle here will be called C.
[tex]c^2=a^2+b^2-2abcosC[/tex]
[tex]c^2=2^2+5^2-(2*2*5*cos60) (cos60=0.5) c^2=4+25-(20*0.5) c^2=29-10 c^2=19 c= \sqrt{c^2} c= \sqrt{19}[/tex]
Let's say, for the sake of solving this problem the side with the length of 2 is a, that with the length of 5 is b, and the unknown is c. The known angle here will be called C.
[tex]c^2=a^2+b^2-2abcosC[/tex]
[tex]c^2=2^2+5^2-(2*2*5*cos60) (cos60=0.5) c^2=4+25-(20*0.5) c^2=29-10 c^2=19 c= \sqrt{c^2} c= \sqrt{19}[/tex]
