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Help a level maths trig q

Help I don’t get part c how to do it
Plz explain the worked answer is here but I don’t get where the numbers came from and how to do it… Ive not much time so plz hurry. What I did was set sin (pi(t) over 12 minus 3) equal to one and got a wrong ans
It’s part c btwIMG_2410.jpegIMG_2411.jpeg
(edited 1 year ago)
Reply 1
Original post by Alevelhelp.1
Help I don’t get part c how to do it
Plz explain the worked answer is here but I don’t get where the numbers came from and how to do it… Ive not much time so plz hurry. What I did was set sin (pi(t) over 12 minus 3) equal to one and got a wrong ans
It’s part c btwIMG_2410.jpegIMG_2411.jpeg

are you happy with part (b)?

sin(something) is a max when "something" = pi/2, basically where sin = 1. So is there anything else you don't understand in the working?
Original post by davros
are you happy with part (b)?

sin(something) is a max when "something" = pi/2, basically where sin = 1. So is there anything else you don't understand in the working?

Yep I get part b just not c
You know the max value for sin must occur when the argument is pi/2 +/- multiples of 2pi. You also know that the answer must be around t=12 as its asking about the hottest time of day (after midnight). Your argument for sin is
pi*t/12 - 2
(roughly), so that equals pi/2 ~ 1.5 when
pi*t/12 = 1.5 + 2
t = 12(3.5)/pi ~ 12

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