A right angle equal to half the length of the hypotenuse faces an angle of 30. Set in the right triangle ABC, ∠ BAC = 90, AB= 1/2BC. Proof ∠ ACB = 30. It is proved that 1 extends BA to D, making AD=AB and connecting CD. ∵∠BAC = 90°, AB=AD, ∴AC bisects BD vertically, ∴BC=CD (the distance from the point on the middle vertical line to both ends of the line segment is equal), ∵AB= 1/2BC, AB = AD =1/. Proof 2 takes the midpoint d of BC and connects AD. ∫∠BAC = 90, ∴AD= 1/2BC=BD (the midline of the hypotenuse of a right triangle is equal to half of the hypotenuse), ∫ab = 1/2bc, ∴△∴ab=ad=bd.