If the 3 sides of a triangle are a, b, c, then
[tex]a^2+b^2Then the triangle is an obtuse angle triangle[tex]a^2+b^2=c^2[/tex]
Then the triangle is a right-angled triangle
[tex]a^2+b^2>c^2[/tex]
Then the triangle is an acute angled-triangle
Note that c is the longest side
Let us check our sides
[tex]\begin{gathered} \because11^2=121 \\ \because9^2=81 \\ \because8^2=64 \\ \because81+64=145 \end{gathered}[/tex]
That means 145 > 121
[tex]\therefore a^2+b^2>c^2[/tex]
The triangle is an acute angled-triangle
