Question

Write an equation for a sine curve that has the given amplitude and period, and which passes through the given point.

Answer 1

ANSWER

$y = 5\sin( \frac{\pi}{3} x - \frac{2\pi}{3} )$

EXPLANATION

Let the equation of the sine curve be of the form;

$y = a \sin(bx + c)$

where a=5 is the amplitude and period,

$\frac{2\pi}{b} = 6$

This implies that

$b = \frac{2\pi}{6}$

$b = \frac{\pi}{3}$

We substitute the values we got so far into our equation to obtain;

$y = 5\sin( \frac{\pi}{3} x + c)$

When we substitute (2,0) we obtain;

$0= 5\sin( \frac{2\pi}{3} + c)$

Solve for c.

$\sin( \frac{2\pi}{3} + c) = 0$

$\frac{2\pi}{3} + c = \sin^{ - 1} (0)$

$\frac{2\pi}{3} + c = 0$

$c = - \frac{2\pi}{3}$

Hence our equation becomes

$y = 5\sin( \frac{\pi}{3} x - \frac{2\pi}{3} )$

The correct choice is D.