Thread: Trig word problem - solving a trig equation.

I came across a word problem that I can't seem to puzzle through. I know the answer to it, but I can not seem to find out how to get to it.

"A block is set in motion hanging from a spring and oscillates about it's resting position x=0, according to the function . For what values of t is the block at it's resting position x=0."

This is how I've worked it so far.

















This answer, unfortunately, is not correct. I know that the correct answer is 75 degrees, but I have no clue how to get to that answer.

Any help would be appreciated. I've been puzzling over this question for a while now.

It's because if then ...

Originally Posted by Prove It

It's because if then ...

Your completely correct. Not sure why I forgot about the negative sign, as I had it on the paper I was typing from. However, it still turns out as -15 deg, which doesn't work.

There will be a solution for in the second quadrant and the fourth quadrant.

Oh, now I'm even more confused. The solution that the book gives is either , or , which are in quadrant one.

Because when you have the values of , you need to divide them by to get the values of ...

Ah, I understand now. I think I had some faulty notions at play. I was approaching the negative degree as when the spring was below the zero, but I guess the motion is always positive around the unit circle, hence the reason I had to get rid of the negative? Still having a hard time wrapping my head around the underlying concept, but it should click in soon.

Once again, Prove It, you have helped immensely. Thank you.
Now when I get home I am going to post a problem that has sin as an exponent, and I haven't got a clue. Not sure why this chapter in the book is so difficult for me.