Signal Voltage

Hi all, this is my first post

I'm doing HNC Electrical Engineering and I've come across this one question that im struggling with a little.

You know that the signal takes the following form:
𝑣 = 𝑉𝑝 sin (2𝜋 ft − ∅)

Taking measurements from the oscilloscope display above, determine 𝑉p, 𝑓,and ∅, and insert those values into the above equation.

Now rearrange your new equation to make the time t, the subject of this formula and hence determine, to within 3 decimal places, the first point in time when the voltage waveform has a magnitude of 5.25
volts.
Assuiming 𝑣 = 5.25

I have rearranged the formula:
t = asin((5.25/7)+∅)/2𝜋(f)

Am I along the right lines? Any help would be appreciated.

Hi all, this is my first post
I'm doing HNC Electrical Engineering and I've come across this one question that im struggling with a little.
You know that the signal takes the following form:
𝑣 = 𝑉𝑝 sin (2𝜋 ft − ∅)
Taking measurements from the oscilloscope display above, determine 𝑉p, 𝑓,and ∅, and insert those values into the above equation.
Now rearrange your new equation to make the time t, the subject of this formula and hence determine, to within 3 decimal places, the first point in time when the voltage waveform has a magnitude of 5.25
volts.
Assuiming 𝑣 = 5.25
I have rearranged the formula:
t = asin((5.25/7)+∅)/2𝜋(f)
Am I along the right lines? Any help would be appreciated.

Hi, it looks like I am doing the same course as you. What figure did you settle on for t1? The exact point at which the wave crosses the midline is a bit ambiguous....

My advice is to do algebra first, then substitute numbers later.