Originally Posted by

**Rich B.** aussiekid90:

Note that solutions found by T*hePerfectHacker *and *ticbol *are equivalent. The latter solution, i.e., y = 98.6 +(0.3)sin(15t -165), simplifies to y = 98.6 +(0.3)sin(15t + 15), as sin(u)=sin(u+180) for all real u. The argument (15t + 15) being expressed in degrees converts to ((pi/12)(t) + pi/12) in radian measure (15° = pi/12 radians). Hence the equation is equivalent to y = 98.6 +(0.3)sin((pi/12)(t) + pi/12), which is identical to the solution presented by P.Hckr..

One need only remember to set one's calculator to radian mode if evaluating sin[(pi/12)(t)+pi/12], and to degree mode when working sin(15t+15).

I just didn't want you to go nuts trying to figure out which of the two presentations is correct and, consequently, the one you should focus upon. They are both correct.

Regards,

Rich B.