# lenghts

1. ### Relation between cosines and lenghts of triangle

Prove that in any triangle we have the following relation \frac{a+b+c}{R}=8\cos{\frac{A}{2}}\cos{\frac{B}{2}}\cos{\frac{C}{2}}
2. ### calculating the effect of inaccurate triangle vertex positions on the edge lenghts

i'm not sure how to solve the following problem: i have a triangle with each of the three known vertex positions A,B,C being inaccurate, meaning they can each deviate up to certain known radii rA, rB, rC into arbitrary directions. given such a triangle, i want to find out how much the...
3. ### lenghts of sides triangle

Hello, Can you tell me how to find the sides of he triangles in Q1 and Q2 in the attached drawing they are right angled triangles in question 2 i found that a=1.9 and b=1.3 using Soh but i want to know If i can use a^2 = b^2 + c^2 - 2bc(CosA) I want to be able to use other forumlas than...
4. ### Angle A when three lenghts are known

Angle A when three lengths are known Hi, Can anybody tell me the formula for getting an angle A when I have the lengths of the 3 sides of a triangle. Ive forgotten how to do it. Thanks for the help