0/2011 (a)
Prove that cos3x = 4cos'x - 3cos x. Hence, show that
cos2x =-(cos 6x + 3cos 2x).
(b)
[4 marks]
Use the above identity to find all the solutions in the interval
-180° <x<180° of the equation 2 cos 3x + cos2x+1= 0. [7 marks]

need more information

step-by-step explanation:

c. side angle side. u shares the same sides

hello from mrbilldoesmath!

answer:   (7x + 6y) ( 49x^2 - 42xy + 36y^2)

discussion:

in general, the factorization of a^3 + b^3 is

a^3 + b^ 3 = (a + b) ( a^2 - ab + b^2)

in our case note that 343 = 7^3 and 216 = 6^3 so the equation becomes:

343x^3 + 216y^3 = (7x)^3 + (6y)^3

if you think of a (above) as 7x and b as 6y the factorization becomes

343x^3 + 216y^3 =

((7x + 6y) (   (7x)^2 - 7x*6y + (6y)^2)   =

(7x + 6y) ( 49x^2 - 42xy + 36y^2)

you,

mrb

(a + b) (a^2 - a b + b^2)

answer: graph 2

step-by-step explanation: