Trigonometry (Period/ Amplitude/ Graph)

(CIE 0606/2020/w/11/Q2)
(a) Write down the amplitude of $1+4\cos \left(\dfrac{x}{3}\right).$

(b) Write down the period of $1+4\cos \left(\dfrac{x}{3}\right).$[1]

(c) On the axes below, sketch the graph of $1+4\cos \left(\dfrac{x}{3}\right)$ for -180°$\le x\le $180°.

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*********math solution************* (a) Amplitude=4 (b) period=$\dfrac{360}{\frac 13}=360\times 3=1080^{\circ}.$ (c) **********end math solution********************