The correct options are
A Period of f(x) is 2π3
B a=−1
C b=3
D a=1
There are two zeros that delimit half a cycle.
Hence, half a period is equal to:
−π8−(−11π24)=π3
Therefore, period of f(x) is
P=2×π3=2π3
But,period of f(x)=acos(bx+c) is 2π|b|
So, 2π3=2π|b|
⇒b=±3
⇒b=3(∵b>0)
The range of f(x)=acos(bx+c) is [−a,a]
From graph, the range of f(x)=acos(bx+c) is [−1,1]
So, a=±1