Acute

In math, the word 'acute' refers to an angle less than 90°, or to a shape involving angles less than 90°.
It is the opposite of obtuse, which refers to an angle greater than 90°.

1.Acute angle

Any angle with a measure less than 90°, for example:

For more on this see Acute angle definition.

2. Acute triangle

A triangle where all interior angles have a measure less than 90°, for example:

For more on this see Acute triangle definition.
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