a word problem and a trig question

[Guest]

In an electrical circuit, the voltage, V vols as a function of time, t minutes, is given by V= 12-9t + 2t^2. Determine the greatest and least values f voltage during the first 5 minutes when do the values occur??






If sine of an angle is 0.3781, can the angle be obtused? Explain.
How would you explain this question?

 

[tkhunny]

In an electrical circuit, the voltage, V vols as a function of time, t minutes, is given by V= 12-9t + 2t^2. Determine the greatest and least values f voltage during the first 5 minutes when do the values occur??

Notice the quadratic form. Have you ever seen the equation of a parabola? Frankly, if you don't shut that thing off, we're all in trouble eventually.

Vertex (t-value for max or min), given A*t^2 + B*t + C, is -B/(2*A). This gives t = 9/(2*2) = 9/4. Since A > 0, this is the location of the Minimum value. Find V(9/4) to determine the minimum value.

As for the maximum, how far from the minimum can you get? As you get farther from the absolute minimum, these things ONLY increase.

Toward Zero
9/4 - 0 = 9/4
Toward 5
5 - 9/4 = 20/4 - 9/4 = 11/4. Check out t=5 for the maximum.

If sine of an angle is 0.3781, can the angle be obtused? Explain.
How would you explain this question?

Ummm...Is "obtuse" a verb?

Perhaps you could examine this relationship: sin(x) = sin(pi-x).