Answer:
[tex]F_{1}[/tex] = 5
Step-by-step explanation:
Given [tex]F_{1}[/tex] is perpendicular to [tex]F_{2}[/tex] then Δ ABC is right
Given [tex]F_{2}[/tex] = [tex]F_{1}[/tex]
Then using Pythagoras' identity in the right triangle
[tex]F_{1}[/tex] ² + [tex]F_{2}[/tex] ² = (5[tex]\sqrt{2}[/tex] )² , that is
2[tex]F_{1}[/tex] ² = 50 ( divide both sides by 2 )
[tex]F_{1}[/tex] ² = 25 ( take the square root of both sides )
[tex]F_{1}[/tex] = 5
