Question

It's given: y=-5+7cos(3a-9).From which of the following values the function takes maximum:
a) -177 degrees
b) -123 degrees
c) 0 degrees
d) 111 degrees

Answer 1

0 wins the plug and play

Answer 2

O.o I thought it should be cos(3a-9)=1
and u had to find a
but I didn't get 0....
how did u do tht?Explain pls????????

Answer 3

i just plugged in the values of the answers into the equaton to see which one was the biggest

Answer 4

another way is to just go by the 3a-9 part and see which angles higher on the unit circle

Answer 5

wouldn't it b 3*0-9=-9?
how do u find it's cos? O.o

Answer 6

the cos of any angle gets smaller as you move from 0 up to 90; and also from 0 to -90; so that largest 'value in that will get your biggest number right?

Answer 7

cos(-9) is bigger than cos(10) by reason that 10 produces a steeper angle that has a cosine value closer to 0 than to 1

Answer 8

oh......I got it....Thanks :):):) smth else pls....what does that guru mean?:)))

Answer 9

3(-177)-9
-531-9 = -540; spin out 360 to get it to; -180

cos(-180) = -1

3(-123)-9
-369-9 = -378; spin out a 360 to get it to; -18

cos(-18) is between 0 and 1

3(0)-9 = -9

cos(-9) is closer to 1 than cos(-18)

3(111)-9
333-9 = 324; to keep things the same spin out 360 to get; -36

cos(-36) is even farther away from 1 than cos(-9)

so the largest value for the cos(...) part is obtained at a=0

which then gives you the largest value for the entire equation

Answer 10

I've always hated trigonometry :(:(:( Thank you veeeeeeryyyy much :):)

Answer 11

this might splain it better :)

Answer 12

Yes it does :):) ^_^ Thnx :):)