Current location - Training Enrollment Network - Mathematics courses - The Theorem of Triangle Internal Angle Sum in Junior Two Mathematics and Its Proof
The Theorem of Triangle Internal Angle Sum in Junior Two Mathematics and Its Proof
1:∠DBC+∠C = 90∠C =( 180-∠A)/2∠DBC+( 180-∠A)/2 = 90

Yes: ∠DBC=∠A/2

2: CE is the midline on the hypotenuse AB, so CE=AB/2 AB=2AC, so CE=AC.

Because AB=2AC, ∠B=30 ∠A=60, the triangle ACE is an equilateral triangle, and CD is high, so CD is also an angular bisector, so ∠ECD=30.