C3 question Watch
Q) Calculate the maximum value of H predicted by this model and the value of t, to 2 decimal places, when this maximum occurs. 
I don't really have much clue where to start on this, it's quite tragic lol... I was thinking about when sin and cos are maximum but a train hit me through the light at the end of the tunnel. Any help will be much appreciated, thank you.
If you were to plot a graph of H against t, then I guess you'd get some sort of curve between 0 <= t < 12. What would you do to find the value of the maximum point of this curve?
wait no, there's no coordinates to play around with
make that equal to zero
you'll get an equation with sin and cos equal to zero
you can make sin of blah equal to cos of blah
divide to get tan of blah equal to something and solve for t.
put that back into H to find the maximum
2 sin theta - 1.5 cos theta = 2.5 sin (theta - 0.6435)
Can this be used in any way? Question is a 3 marker, surely it's too much work for 3 marks? But I've started following your methods :]
I just did it
H = 6 + 2sinA - 1.5cos A where A is 4pit/25
so we can use what you've got from the earlier question to find what dH/dt is when equal to zero
so H = 6 + 2.5sin(A - 0.6435)
dH/dt = 10pi/25. cos(A-0.6435)
when dH/dt = 0
cos(A-0.6435) = 0
you can solve for t now
Thanks for the help both of you... the second I get my daily rep allowance I'll make sure you come back and thumbsup your posts.