Question

Urgent
Va rog
Ajutor
Plis​

Answer 1

$\bf (sinB+sinC)^2+(cosB-cosC)^2=\Big(\dfrac{b}{a}+\dfrac{c}{a}\Big)^2+\Big(\dfrac{c}{a}-\dfrac{b}{a}\Big)^2=\dfrac{(b+c)^2+(c-b)^2}{a^2}=\\ \\ \\ =\dfrac{b^2+2bc+c^2+c^2-2bc+b^2}{a^2}=\dfrac{2(b^2+c^2)}{a^2}\stackrel{TP}{=}\ \dfrac{2a^2}{a^2}=2\in\mathbb{Z}$