if AE is a bisector of angle BAC and a triangle ABC and AD perpendicular BC then prove that angle DAE is equal to 1/2(angle B- angle C
Answers
Answer:
∠DAE = 1/2(∠C − ∠B)
Step-by-step explanation:
Given:-
In ∆ABC;
AE is a bisector of ∠BAC
AD perpendicular BC
To Prove:-
∠DAE = 1/2(∠C − ∠B)
Proof:-
In ∆ABC, since AE bisects ∠A, then
∠BAE = ∠CAE (i)
In ∆ADC,
∠ADC+∠DAC+∠ACD = 180° [∵Angle sum property]
⇒90° + ∠DAC + ∠C = 180°
⇒∠C = 90°−∠DAC (ii)
Now,
In ∆ADB,
∠ADB+∠DAB+∠ABD = 180° [∵Angle sum property]
⇒90° + ∠DAB + ∠B = 180°
⇒∠B = 180°-90°−∠DAB (iii)
⇒∠B = 90°−∠DAB
Subtracting (iii) from (ii), we get;
∠C − ∠B =∠DAB − ∠DAC
⇒∠C − ∠B =[∠BAE+∠DAE] − [∠CAE−∠DAE]
⇒∠C − ∠B =∠BAE+∠DAE − ∠BAE+∠DAE [∵∠BAE = ∠CAE ]
⇒∠C − ∠B = 2∠DAE
⇒ ∠DAE = 1/2(∠C − ∠B)
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