Question

Find all the angles between 0 degree and 360 degree which satisfy 4sin x = 2 cos2x - 3

Answer 1

Do i need to use double angle formula?

Answer 2

which should i use?

Answer 3

note that \(\cos 2x=1-2 \sin^2 x\)

Answer 4

noted thanks.

Answer 5

very well...:)

Answer 6

carry on please /

Answer 7

well make a quadratic equation in terms of \(\sin x\)

Answer 8

i get this 2 sin^2 x + 4 sin x = -1

Answer 9

then i take out common factor is that right?

Answer 10

emm...yeah solve it by quadratic formula or factoring...which one u are comfortable with

Answer 11

My answer are x = 270 degree and 315 degree

Answer 12

is that correct?

Answer 13

let me check it...

Answer 14

\(4\sin x = 2 \cos 2x - 3 \) -----> \(4\sin x+4 \sin^2 x = -1\)

Answer 15

or \( (2 \sin x+1)^2=0 \) and it gives \(\sin x=-1/2 \)

Answer 16

so 210 and 350

Answer 17

oh i see what you did there >.>

Answer 18

can you wait for awhile coz i have another question :(

Answer 19

i think u made a little mistake in making quadratic equation...