Definition
Obtuse triangle
An obtuse triangle has one interior angle larger than a right angle.
Continue from this idea into connected AXIO math.
What it means
One corner opens wider than a square corner. That angle is obtuse. The other two angles must be acute, because all three interior angles of a triangle add to 180°.
Remember it
Spot the one corner that opens wider than a 90° right angle.
Example
A triangle has angles 35°, 45°, and 100°. They total 180°, and 100° is greater than 90°, so the triangle is obtuse.
Watch for
A triangle with a 90° angle is a right triangle, not an obtuse triangle; the wide angle must be greater than 90°.
Common mix-up
“Obtuse angle” names one angle. “Obtuse triangle” names the whole triangle because one of its interior angles is obtuse.
Exact meaning
An obtuse triangle is a triangle with exactly one interior angle greater than 90° and less than 180°.