# Conjugate function reverse angle in a neighborhood

Can you please help me with this question. Prove that if conjugate of $F$ is analytic in a neighborhood of $z_0$ in $C$ then $F$ reverses angles at $z_0$. Can anyone please explain that for me? what does it mean to reverse an angle here? Thanks in advance...

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Any two curves intersecting at a point will have two tangent vectors at this point; a function takes curves to curves, points to points, intersections to intersections, tangent vectors to tangent vectors. Your task it to show the angle between two tangent vectors remains the same (in an absolute sense), but the two vectors get reversed in orientation. –  anon Sep 18 '12 at 3:01
To prove it I can find the cauchy Riemman equatio for the conjugate, but then I`m not sure how to finish the proof. Any help? –  Danny Sep 18 '12 at 3:59