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I have this problem to solve:

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The translation is:

Been the next angles: $\angle ABC$, $\angle DEF$ and $\angle GHI$, if $\angle ABC$ is "Parallel?" to $\angle DEF$ and $\angle GHI$ is parallel (again?) to the other 2 angles, then compute the measure of $\angle DEF$ if m(GHI)=75 grades.

But, obviously there are errors in it. What do not make sense to me is section marked in blue. $\angle ABC$ "Parallel?" to $\angle DEF$ and almost immediately again something that makes me think in Parallel angles.

Do I miss something here? How can an angle be "parallel" to another? Are they flat angles? ($180^\circ$)

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  • $\begingroup$ Skallab , can you please write the question (translated form )yourself instead of pasting pictures. It's hard to read . $\endgroup$ Commented Aug 3, 2013 at 0:22
  • $\begingroup$ Making a simplification of the question is suppose it can be reduced to this: what means two parallel angles? In other words ABC//DEG express something like parallel angles. Do this exist? or I misunderstood the two parallel lines in-between the 2 angles $\endgroup$ Commented Aug 3, 2013 at 0:32

1 Answer 1

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I just receive this theorem:

Theorem 2.3

Been 3 rect lines R1, R2 and R3 in which R1 is parallel to R2 and R3 intersects R1 and R2. And being a and b two alternate-external opposites angles. Then a=b

We can say that a and b are PARALLEL ANGLES

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Also I have this:

Definition 2.3 Been 2 angles a and b if their sides are perpendiculars "in pairs" we can say that both angles are perpendicular angles. If their sides are parallel "in pairs" then we say that both angles are parallels

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Do anyone has any comment?

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