Hello :
<span>A(-2, -5), B(-3, 2), and C (1, -2)
calculate : AB² , AC² ,BC²
</span> AB² = ( -3 +2 )² + ( 2 +5 )² =50
AC² = ( 1 +2 )² + ( -2 +5 )² =18
BC² = ( 1 +3 )² + ( -2 - 2 )² = 32
by petagor rule : AB² = AC² + BC²....(<span>ABC is a </span>right triangle in : C )
CosA = AB/AC = 55/73 ≈ 0.7534
m∠A ≈ 41.11°
First, let's multiply the first equation by two on the both sides:
<span>8x + 7y = 39 /2
</span>⇒ 16x + 14y = 78
Now, the system is:
<span>16x + 14y = 78
</span><span>4x – 14y = –68
</span>
After adding this up in the column:
(16x + 4x) + (14y - 14y) = 78 - 68
20x = 10
⇒ x = 10/20 = 1/2
y can be calculated by replacin the x:
<span>8x + 7y = 39
</span>⇒ 8 · 1/2 + 7y = 39
4 + 7y = 39
7y = 39 - 4
7y = 35
⇒ y = 35 ÷ 7 = 5
