The length of the unknown side of the triangular frame is 7 ft.
What is a triangle?
"A simple closed curve or a polygon formed by three line-segments (sides) is called a triangle."
From the drawn triangle
According to the law of cosines
[tex]x^{2} =3^{2} +5^{2} +2[/tex] × [tex]3[/tex] × [tex]5[/tex] × [tex]cos 120^{0}[/tex]
⇒ [tex]x^{2} =9+25+2[/tex] × [tex]3[/tex] × [tex]5[/tex] × [tex]\frac{1}{2}[/tex]
⇒ [tex]x^{2} = 9+25+15[/tex]
⇒ [tex]x^{2} = 49[/tex]
⇒ [tex]x = \sqrt{49}[/tex]
⇒ [tex]x = 7[/tex]
Hence, the length of the unknown side of the triangular frame is 7 ft.
Learn more about triangle here
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