Given two angles and the opposite side of one angle, how to make a triangle

Given two angles and the opposite side of one angle, how to make a triangle

Given a, a, B, make triangle
Method:
(1) Make a triangle a'bc 'of any size such that angle B = known angle B and angle a' = known angle A
(2) Take point B as the center of the circle, a as the radius, draw an arc, and cross BC 'or its extension line at C,
Make a parallel line of a 'C' through C and cross Ba 'or its extension line to a
Get the triangle ABC, which meets the requirements of the topic

If the intersection of the vertical bisectors of the three sides of a triangle is in the triangle, then the triangle is ()
A. Obtuse triangle B. right triangle C. acute triangle D. isosceles right triangle

∵ the intersection of the vertical bisectors of the three sides of a triangle is in the triangle, and the triangle is an acute triangle

Why is the angle of the focus triangle in the ellipse maximum when the moving point is in the middle

Let a ∈ ellipse (X & sup2; / A & sup2; + Y & sup2; / B & sup2; = 1, a > b > 0), AF1 = D, af2 = f, ∠ f1af2 = α, from cosine theorem: cos α = {D & sup2; + F & sup2; - 4 [A & sup2; - B & sup2;]} / (2DF), ∵ D & sup2; + F & sup2; = 4A & sup2; - 2dfcos α = [4B & sup2; / (2D

Triangle circumcircle is the focus of triangle, how to prove?

Find any two sides of a triangle and make the vertical bisector of the two sides. The two points intersected by the bisector are the outer center of the triangle. Make a circle with the distance from the outer center to one side. This circle is the circumscribed circle of the triangle
The center of a circumscribed circle is the center of a triangle