Question

solve for x: sin3x=-cosx

Answer 1

it is sin^3 or just sin3x???

Answer 2

sin3x..... Its not raised to the power of 3

Answer 3

sin(3x) = sin(x+2x)
this help?

Answer 4

you have 2 identities to deal with

Answer 5

@gopZ

Answer 6

Cos(90-3x)= -cosx
, because cos90-x=sinx ryt?

Answer 7

yes and
-cos(x) = cos(180-x)
so
90-3x = 180 - x
solve for x

Answer 8

but that only captures 1 of 3 solutions

Answer 9

Then lets find the general solution

Answer 10

sorry for delay...here use sum to product identity
http://en.wikipedia.org/wiki/Trig_Identity#Product-to-sum_and_sum-to-product_identities

\[\cos(90-3x) + \cos x = 0\]
\[2\cos(\frac{90-2x}{2}) \cos(\frac{90-4x}{2}) = 0\]
\[\cos(45-x) \cos(45-2x) = 0\]
...

Answer 11

@dumbcow, ive been trying to award you with a medal but dis freakin' phone im using does not work properly with dis site! Anyway thanx for ur help

Answer 12

haha no worries :)