BAC is the given angle.
Build the angle, using Angle.
Then, build a circle, centered in A and with radius less than the angle sides length, using Circle with center point, to intersect the angle sides in E and D.
Now, build two circles, having the same radius of the previous one, using Circle with center point, the first centered in E (and radius EA), the second centered in D (and radius DA).
These two circles have an intersection point I.
Build the halfline starting in A and passing through I, using Halfline.
This halfline is the bisettrice of the given angle BAC, infact, the points A, E, I, D are the vertexes of a rhomb, and AI is one of its diagonals; as in a rhomb the diagonals are also the bisectors of the angles, AI is the bisector of the angle DAE.

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