The teacher told the class that an acute angle was less that 90 degrees.
The wood formed an acute angle with the wall.
any angle less than 90* is acute
Example sentence - The actions of his horrid children caused acute chronic pain for all involved.
You would use a protractor. An acute angle is an angle less than 90°.
The Geometry teacher told us to do the acute angle exercises ..
An equilateral triangle has three acute internal angles. The injection caused acute pain, but only for a moment.
Because his hearing was so acute, he could easily hear what was going on in the next room.
The patient experienced an acute pain in their chest, prompting the medical team to take immediate action.
protracter
She wore her hat at a jaunty angle.
I assume that the second use of the word "triangle" in the question should be angle. An obtuse triangle must have two acute angles.
You can either use a protractor or, if you're given the other angles in a triangle, you can subtract them from 180. An acute angle is an angle less that 90 degrees.