6.23+ -12.49 -2.6= 6.23+ -12.49+ -2.6
-6.26+-2.6= -8.86
Including Jamiz, there are 14 girls in the class. If this if half of the total number of pupils (as half are girls, the other half being boys) the total number of students is 14 × 2 = 28 students
Equate whats inside (arguments)
with base period of sine function
and solve for x to get period,

So the period of the graph of the given function is precisely 2.
Hope this helps :)