Question

CURRENT The current I in amperes for a circuit at time t seconds is given by:
I=40cos[60pi(t+1/120)]
A. Find the maximum current.
B. Find the current after 0.02 seconds.

Answer 1

So if you want to find the maximum current, and you're given I=40*(trig function) then you know that trig functions can only ever oscillate between 1 and -1 no matter how often they wiggle. That means when the trig function is 1, that's when you're at your max, which is 40. That's why they call the number multiplied by the trig function the amplitude, because it is the max value the function can have.

If you want to know the current after .02 seconds, just replace t in the above equation with .02 and solve it by using your calculator, unless your teacher wants you to figure it out by making the angle inside the trig function some multiple of pi that you recognize.

Answer 2

Okay, i totally understand a. But for B, i plug it into the calculator and i get 39.7, while the answer is 23.5

Answer 3

Maybe you're in angles instead of degree mode?

Answer 4

I'm using an fx-85ES they don'y give you a choice.

Answer 5

Hmm, well that's your problem I just plugged it in both ways and got both answers.

Answer 6

really? you got 23.5 for B?

Answer 7

Yeah while in radian mode, since any time you see a pi, you're dealing with radians.

Answer 8

Ohh! that's probably what I did wrong. Lemme try switching pi for 180

Answer 9

Yeah that'll work haha, do that.

Answer 10

got a 32 >.> close enough?

Answer 11

Oh! nevermind, 23.5 :D thanks a ton mn!

Answer 12

No problem haha, glad I could help you figure it out!