Question

triangle ABC is right angled isosceles triangle at B.Then external angle of A is​

Answer 1

AB=BC

angleBAC=angleBCA

and, angle ABC=90

angle(A+B+C)=180

2C+90=180

c=45

angleDAC=angleABC+angleBCA

angleDAC=135

Answer 2

Answer: 135°

Step-by-step explanation:

In an Issoceles right angled triangle the acute angles (angles other than the right angle) are equal.

Now, let the each of the equal angles be x.

We have: 90°+x°+x°=180° [Angle Sum Property]

= 90°+2x°=180°

= x°=(180-90)°/2

= x°=45°

Hence measure of angle a and c is 45°.

Measure of angle a = 45°

Measure of angle b = 90°

:: External Angle = a°+b° = 45°+90° = 135°