Answer
a) $13 \sin 3 \theta +0.395$
b) $13 \cos 3 \theta -1.176$
Work Step by Step
a) $\sqrt {(12)^2+ (5)^2} \sin 3 \theta + arctan \dfrac{5}{12}=13 \sin 3 \theta +0.395$
b) $\sqrt {(12)^2+ (5)^2} \cos 3 \theta - arctan \dfrac{12}{5}=13 \cos 3 \theta -1.176$
