Calculating the rate of change of voltage when t = 20ms

[htcdesire95]

An alternating current v volts is given by v = 125 sin 80t, where t is the time in seconds. Calculate the rate of change of voltage when t = 20ms

I really need help with this question otherwise ill will fail my course and I will literally be depressed my whole life as I really love the career i want to do.

Answers will truly be appreciated honestly.

Many thanks

 

[Steven G]

An alternating current v volts is given by v = 125 sin 80t, where t is the time in seconds. Calculate the rate of change of voltage when t = 20ms

I really need help with this question otherwise ill will fail my course and I will literally be depressed my whole life as I really love the career i want to do.

Answers will truly be appreciated honestly.

Many thanks

You want rate of change of V where V is a function of time t. So you take the derivative of V with respect to t and then plug in ....

 

[htcdesire95]

You want rate of change of V where V is a function of time t. So you take the derivative of V with respect to t and then plug in ....

so, v(t)= 125/sin(80t)

 

[Steven G]

so, v(t)= 125/sin(80t)

I wouldn't know what v(t) is. Initially you said v(t)= 125 sin 80t and now you say it is v = 125/ sin 80t. So which is it?

 

[htcdesire95]

Calculus

I wouldn't know what v(t) is. Initially you said v(t)= 125 sin 80t and now you say it is v = 125/ sin 80t. So which is it?

Sorry about that im having a terrible day.

it is v(t)= 125 sin 80t

 

[Steven G]

Sorry about that im having a terrible day.

it is v(t)= 125 sin 80t

Now take the derivative of V, that is take the derivative of 125sin80t

 

[htcdesire95]

Now take the derivative of V, that is take the derivative of 125sin80t

v(t)= 125 sin(80t)

= 123.1 t

 

[Steven G]

v(t)= 125 sin(80t)

= 123.1 t

No, 125*sin(80t) is not 125*sin(80)*t =123.1t.
What part of take the derivative do you not get? I will help by saying that the derivative of V is NOT V, it is V '

 

[htcdesire95]

No, 125*sin(80t) is not 125*sin(80)*t =123.1t.
What part of take the derivative do you not get? I will help by saying that the derivative of V is NOT V, it is V '

aha. so, v'= 125 cos(pie/18)

 

[Steven G]

aha. so, v'= 125 cos(pie/18)

Where did pi/18 come from. When you take the derivative of any trig function the angle never changes.
You need to know that derivative of sin(u) is cos(u)*u'
If you do not get this then you really need to think about not being in calculus. Just get better prepared and come back and ace calculus. Actually the calculus part of calculus is quite easy, almost trivial. What beats most students is that calculus demands that you know algebra and trigonometry well and many students do not know it well enough to survive calculus.