I would like to duplicate this graph:

I've used this code to draw the circle:

Graphics[{Circle[{0, 0}, 3, {-2Pi, 2Pi}]},PointSize[.025]]


But Mathematica complains about improperly formatted options, and I don't know how to proceed from here.

• Andrea, your problem was that you put the PointSize out of place. This works: Graphics[{PointSize[.025], Circle[{0, 0}, 3, {-2 Pi, 2 Pi}]}]. Your question was put on-hold as it seems to be off-topic, i.e it arises from a simple mistake (syntax error) and is unlikely to help any future visitors as it answer is easily found in the documentation. Don't be discouraged by that cleaning-up policy. Your future good questions are welcome. Learn about common pitfalls here. – rhermans Jun 1 '18 at 14:42

Graphics[{{Green, Line[{{0, 0}, {1/Sqrt[2], 1/Sqrt[2]}}]}, {Red,
Line[{{1/Sqrt[2], 0}, {1/Sqrt[2], 1/Sqrt[2]}}]}, {Line[{{0, 1/Sqrt[2]},
{1/Sqrt[2], 1/Sqrt[2]}}]}, {Green, PointSize[.03],
Point[{1/Sqrt[2], 1/Sqrt[2]}]}, {Circle[{0, 0}, 1, {-2 Pi, 2 Pi}]}},
Axes -> True, Ticks -> {{0, 1/Sqrt[2]}, {0, 1/Sqrt[2]}}]


• I added a picture & fixed formatting, I hope you don't mind :) – Öskå May 18 '14 at 16:00
• @Öskå that is ok. thanks – Basheer Algohi May 19 '14 at 4:14

Such plane figures are amenable to using complex numbers instead of pairs of reals for their points, and hence readily drawn using David Park's Presentations add-on (http://home.comcast.net/~djmpark/DrawGraphicsPage.html):

Draw2D[{
ComplexCircle[0, 1],
Green,
ComplexLine[{0, (1 + I)/Sqrt[2]}], PointSize[0.025], ComplexPoint[(1 + I)/Sqrt[2]],
Red,
ComplexLine[{1/Sqrt[2], (1 + I)/Sqrt[2]}], ComplexLine[{I/Sqrt[2], (1 + I)/Sqrt[2]}]
},
Axes -> True, Ticks -> {{1/Sqrt[2]}, {1/Sqrt[2]}}]