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 angles are less than \(90^{\circ}\). So, if triangle \(RST\) is acute, then each angle (\(\angle R\), \(\angle S\), \(\angle T\)) must satisfy the condition of being less than \(90^{\circ}\).

Answer:

less than \(90^{\circ}\)