Given that point O is the center of circumscribed circle of triangle ABC, tangent AC length is 4, AB length is 2, then vector AO * vector BC =?

Given that point O is the center of circumscribed circle of triangle ABC, tangent AC length is 4, AB length is 2, then vector AO * vector BC =?

Method 1: establish a coordinate system with o as the origin
Let a (rcosu, rsinu), B (rcosv, rsinv), C (rcosw, rsinw); 0

As shown in the figure, in △ ABC, ab = AC = a, BC = B (a ＞ b), in △ ABC, make ∠ CBD = ∠ a, ∠ DCE = ∠ CBD in turn, then De is equal to ()
A. b2aB. ab2C. b3a2D. a3b2

If the inscribed circle of RT triangle ABC is tangent to the hypotenuse BC at point D, and tangent to the two right angle sides at point E.F, then ∠ EDF=
Thank you for waiting online

45 degrees, because the quadrilateral oeaf is a rectangle!

Is there any formula for finding the radius of inscribed circle of right triangle?

Right angle side a, B, hypotenuse C
Radius of inscribed circle r = (a + B-C) / 2