Maths help please (1 Viewer)

[miniwaybzz]

hey guys can some1 please explain this solution part ii )

for this question part ii)

i dont get were the hell 1 - 0.7 = 0.3 comes from and also how sin pi t /6 = -1

 

[aphorae]

minimum value of sin pi/6 t is -1 (i.e. the minimum for any sin function)

therefore min h = 1+ 0.7(-1) = 1 - 0.7 = 0.3

therefore
0.3 = 1 + 0.7sin pi/6 t
-0.7 = 0.7 sin pi/6 t
sin pi/6 t = -1

 

[asianese]

You need to draw the graph! Draw it and come back =)

 

[miniwaybzz]

ahhokay i get it coz all values of sin lie between -1 and 1.... would another method be finding the stat points using calculus? it doesnt seem to work for me.... (maybe im just differentiating wrongly)

You need to draw the graph! Draw it and come back =)

yeh i got it that way but i honestly prefer analytical method

 

[aphorae]

yes you can use calculus but it will take longer, and it will give you BOTH the maximum and minimum values:

dh/dt = pi/6 x 0.7cos pi/6 t
let dh/dt = 0 for turning points

pi/6 x 0.7cos pi/6 t = 0
cos pi/6 t = 0
pi/6 t = pi/2, 3pi/2
t = 3, 9

then you have to test them and explain