Answer
a) $y=-\sin(4x)$
b) $y=-\cos(2x)$
c) $y=5\sin(3x)$
Work Step by Step
Using the even-odd identities we can rewrite the expressions with positive values for $b$.
Solving a,
$y = \sin(-4x)$, using the identity $\sin(-\theta)=-\sin\theta$
$y=-\sin(4x)$
Solving b,
$y=\cos(-2x)$, using the identity $\cos(-\theta)=-\cos\theta$
$y=-\cos(2x)$
Solving c,
$y=-5\sin(-3x)$, using the identity $\sin(-\theta)=-\sin\theta$,
$y=-5\times-\sin(3x)$, multiply the signs.
$y=5\sin(3x)$
