In The diagram above, how many triangles are there?
Count The Triangles (With Labels)
Label the vertices as shown in the diagram on the right.
Now list the triangles using the letters at the corners, for example $\triangle ADE$ is a triangle. The symbol '$\triangle$' before the $\displaystyle ADE$ is just read as 'triangle'. You should put the symbol before the triangles you list, so your list might start:
$\displaystyle \triangle ACE,\triangle ADE,$
Now, which of the triangles you have listed are congruent to each other?
Which of the triangles you have listed are similar to each other but are not congruent?
Do any of the triangles have an obtuse angle (an angle greater than 90 degrees)?