# Answer to Question #9698 in Trigonometry for Fred

Question #9698

In a triangle, Angle "A" is known, and the length of the two adjoining sides. How to find the length of the third side?

Expert's answer

we can use cosine theorem so (length of the third side)^2= (length of the first

side)^2+(length of the second side)^2-2*(length of the first side)*(length of

the second side)*cos(A)

length of the third side=sqrt[ (length of the first

side)^2+(length of the second side)^2-2*(length of the first side)*(length of

the second side)*cos(A) ]

side)^2+(length of the second side)^2-2*(length of the first side)*(length of

the second side)*cos(A)

length of the third side=sqrt[ (length of the first

side)^2+(length of the second side)^2-2*(length of the first side)*(length of

the second side)*cos(A) ]

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