Question

If in a triangle ABC angles A, B, C are in A.P then B
=A+C/2 and B=60 degrees
​

Answer 1

Answer:

Correct option is

D

b

2

=a

2

+c

2

−ac

Let the angles be a,a+d,a+2d. Then

a+a+d+a+2d=180

o

a+d=60

o

So, ∠B=60

o

,

By cosine formula,

cos(B)=

2ac

a

2

+c

2

−b

2

⇒

2

1

=

2ac

a

2

+c

2

−b

2

⇒b

2

=a

2

+c

2

−ac

Hence, D is correct.