Answer: amplitude \(1\); period \(540^\circ\).

The key point is to identify the important features of the graph before using it to answer the question.

(a) The function is

\(\mathrm f(x)=-2+\cos\frac{2x}{3}.\)

The coefficient of the cosine term is \(1\), so the amplitude is

\(1.\)

(b) The period of \(\cos bx\), when \(x\) is in degrees, is

\(\frac{360^\circ}{b}.\)

Here \(b=\frac23\), so the period is

\(\frac{360^\circ}{\frac23}=540^\circ.\)

(c) The graph has centre line \(y=-2\), maximum value \(-1\), and minimum value \(-3\).

It starts at \((0^\circ,-1)\), reaches a minimum at \((270^\circ,-3)\), returns to a maximum at \((540^\circ,-1)\), and reaches another minimum at \((810^\circ,-3)\).