Calculate the length of a side of a triangle knowing

[MathNoob]

Knowing the length of one side of a triangle and the ratio between the other two sides and the angle between the side I know the length of and one of the other sides, how do I calculate the length of that side?

 

[MathLover1]

use cosine law:

 

[MathNoob]

use cosine law:

Shouldnt it be the angle between a and b instead of alpha in the expression?

 

[MathLover1]

in this case yes

in your drawing the angle would be between c and b

since given the ratio between the other two sides, use the ratio a/c

are you given any values for b, a/c, and alpha?

if you know the ratio, whatever fraction it is, numerator is equal to length of side a and denominator is equal to length of side c

 

[MathNoob]

if you know the ratio, whatever fraction it is, numerator is equal to length of side a and denominator is equal to length of side c

I thought the sizes are somehow relative to the angle.
The ratio could be 1/2 or 2/4...

 

[MathLover1]

I thought the sizes are somehow relative to the angle.
The ratio could be 1/2 or 2/4...

if a/c=1/ 2 then c=2a or a=c/2 ; then in formula above, you express a as c/2

whatever the ratio is, use it to express side a in terms of side c

 

[nycmathguy]

if a/c=1/ 2 then c=2a or a=c/2 ; then in formula above, you express a as c/2

whatever the ratio is, use it to express side a in terms of side c

I'm back. I couldn't stay away from math for too long.