general solutions of trig. equations (1 Viewer)

[Dumbarse]

do they ask harder examples of these??, ive only ever done real basic examples at skool. and we just got told to memorise the 3 (sin, cos, tan)

 

[Lazarus]

I've seen small variations, for example, sin(2x) and so on, but I don't think they'd ask for anything beyond that.

 

[Dumbarse]

k kool, thanx

how would u do sin2x??

 

[kini mini]

Solve as you would for x, then divide by two throughout. Be careful with the domain of x though.

 

[rokkuran-x]

we had this one the other day

find the general solution for

cos 54 cos x + sin 54 sin x = sin 2x

x = 36 i think

 

[lolokay]

lol over 6 year old thread


cos 54 cos x + sin 54 sin x = sin 2x
cos(54 - x) = cos(90 - 2x)

now cos(54 - x) = cos(54 - x + 360*n) = cos(x-54 +360*n)
so 90 - 2x = 54 - x + 360n
x = 36 + 360n

or 90 - 2x = x-54 +360*n
3x = 144 + 360n
x = 48 + 120n