Question

if triangle rst is an acute triangle, then ( mangle s ) must be
○ less than ( 90^circ ).
○ equal to ( 90^circ ).
○ equal to ( 100^circ ).
○ greater than ( 90^circ ) and less than ( 180^circ ).

Explanation:

An acute triangle is defined as a triangle where all three interior angles are acute angles. An acute angle is an angle that measures less than \(90^\circ\). So, in triangle \(RST\) (an acute triangle), each angle (including \(\angle S\)) must be less than \(90^\circ\). An angle equal to \(90^\circ\) is a right angle (right triangle), an angle equal to \(100^\circ\) or greater than \(90^\circ\) and less than \(180^\circ\) is an obtuse angle (obtuse triangle), which do not fit the definition of an acute triangle.

Answer:

less than \(90^\circ\)