# Cosine rule help!

## Homework Statement

Hello! I've run into a problem at work and need a quick solution! Basically I need to work out the cut size of a curved bar. I have the chord length (650mm) and the radius' (1335mm) Obviously i need to calculate the inner most angle, then multiply my diameter by pi, divide by 360 then multiply by my new found angle to find arc length

## Homework Equations

Cosine rule A=b$^{2}$+c$^{2}$-a$^{2}$$/$2bc

C=∏d

## The Attempt at a Solution

obviously c and b are both equal at 1335mm. so the triangle becomes isosceles

Arc length = ∏x2670/360 x (1335$^{2}$+1335$^{2}$- 650$^{2}$/2x1335x1335)$^{cos-1}$

this equation leaves us at 28.17°

then (2670x∏/360)x28.17=656mm

many thanks, connor.