Normal strain of cable through arc

[coasterguy]

Homework Statement

See attachment

Homework Equations

eAB=(Lf-Lo)/(Lo)

The Attempt at a Solution

Ok, this is not for HW. I am preparing for a mechanics of materials class next semester. I don't understand when CB goes through the 0.3 degree arc, they say the height is still 300mm. Shouldn't it be slightly less than 300mm? If so, then I have only one angle and one non hypotenuse side, I can't figure out how to solve the rest of the new strained triangle.

Thank you!

 

[PhanthomJay]

300 mm is not the height, it is the length of the part of the rod from B to C, which is unchanged after rotation. Then use the law of cosines as shown.