Attachment 24193

Here are two mirrors OD and OE the angle between them is "alpha"

The question is to find angle "beta"

Help Please!

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- June 30th 2012, 09:45 AMTeloAngles Problem
Attachment 24193

Here are two mirrors OD and OE the angle between them is "alpha"

The question is to find angle "beta"

Help Please! - June 30th 2012, 10:58 AMrichard1234Re: Angles Problem
Angle-chasing usually works:

(due to symmetry)

(since OBA + DBC + ABC = 180 deg)

(also due to symmetry)

(since ACB + EC(D) + BC(D) = 180 deg) - June 30th 2012, 11:46 AMTeloRe: Angles Problem
thanks very much but why are <OBA and <DBC equal? they are not similar triangles please explain ;(

- June 30th 2012, 12:02 PMrichard1234Re: Angles Problem
It's because the ray reflects at point B, so the angle of incidence equals the angle of reflection.