Question

find attachment

Answer 1

Which question? 7 or 8?

Answer 2

q8

Answer 3

gimme 5 mins

Answer 4

No problem :)

Answer 5

Substitute f(0)=-1 into equation,
a+bcos(0)=-1

cos(0) = 1

a+b=-1

a=-1-b .........................(1)

Substitute f(pi/2)=7 into equation,

a+bcos(pi) = 7 ........................(2)

Use (1) from a=-1-b into (2)

(-1-b)+b(-1) = 7

b=-4
a=3

Notice that cos(pi) = -1

Answer 6

For (ii),
They say they want to find the x-coordinates, when f(x) "intersects x-axis"

intersects x-axis means y=0
substitude y= 0 into equation

which is 3-4cos(2x)=0

cos(2x)=3/4
then solve

Answer 7

If you have difficulties solving cos(2x)=3/4 let me know

Answer 8

there was a network problem thank u sam :)