c2=2ab‌‌‌‌‌⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅(i) a2+c2=3b2‌‌‌‌‌⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅(ii) Substitute (i) in (ii) equation, we get, a2+2ab=3b2 ⇒(a+b)2+4b2 ⇒a=b,c=√2a ⇒∠A=45∘=∠B and ∠C=90∘