In △ABC, AB = c cm, AC = b cm and CB = a cm. If ∠A = 2 ∠B,then which of the following is true?

$a^2 =b^2 + bc$

Let A = 90

\(\angle\)B = 45

As we know,

In \(\Delta \)ABC

\( {(BC) }^{ 2} \) = \( {(AC) }^{ 2} \) + \( {(AB) }^{ 2} \)

= \( {(a) }^{ 2} \) = \( {(b) }^{ 2} \) + \( {(c) }^{ 2} \)    ..(1)

If \(\angle\)B = \(\angle\)C

So, AC = AB

b = c

from equation (1)

\( {(a) }^{ 2} \) = \( {(b) }^{ 2} \) + c.c

= \( {(a) }^{ 2} \) = \( {(b) }^{ 2} \) + bc.