1. ## Trigonometry

2. Originally Posted by creatively12

a is the amplitude and c is the median value - both are easily obtained from the graph. The period is also easily obtained and you should know that period = 2pi/b (therefore solve for b).

Substitute the values of a, b and c to get the rule for y. Then solve y = 0 for the smallest positive value of x.

All of this stuff should be known well in advance of 2 hours before an exam.