Arizona universities require that all students admitted complete at least four years of math. This means you should be taking math each year, at progressively more challenging levels. What's more important, is that math is often the defining subject area that removes students from consideration for competitive scholarships and admissions.
Deficiencies
Although you should always plan to complete the Sweet 16 courses, you could have up to 1 year missing in the math category and still be admitted (assuming you have completed all the coursework in at least four of the remaining five areas of study, and you are not missing ANY science courses). See deficiencies.
How to Plan for Math
Below is a chart that can provide an idea of which classes a student should be taking each year to complete their four years of math. If a student is in a position to complete more than four years of math, they should take advantage of this opportunity, as it will further develop their logic skills and make their applications even more competitive with other students' when it comes to admissions and scholarship consideration. Extra years are marked with an * in the chart below.
*For the honors and advanced student, the chart assumes the student took algebra and/or geometry before beginning their freshman year.
This chart is only an example of possible course combinations a student might complete. You should always consult your school counselor each year when designing your schedule, and identify yourself as a "collegebound" student.

Freshman 
Sophomore 
Junior 
Senior 

TYPICAL 
Algebra 
Geometry 
Algebra II (Trigonometry) 
PreCalculus or Statistics 
HONORS 
Geometry 
Algebra II (Trigonometry) 
PreCalculus 
Calculus I or Statistics* 
ADVANCED 
Algebra II (Trigonometry) 
PreCalculus 
Calculus I or Statistics* 
Calculus II or Statistics* 