Answer:

Step-by-step explanation:
The reference angle is an acute angle that angle in standard position makes with the positive x-axis.
The given angle in radians is

This angle is already acute and hence it is itself a reference angle.
The reference angle of any angle in the first quadrant is the same angle.
Answer:
Girls in Mr. Chang's class: 28 - 21 ; # girl students = # total students - # boy students ; 7 girl students.
Boys in Mr. Chang's class: 28 - 7 ; # boy students = # total students - girl students ; 21 boy students.
Answer:
Square
Step-by-step explanation:
square - (geometry) a plane rectangle with four equal sides and four right angles