Need help from Maths people (1 Viewer)

[karen88]

this is a question i couldn't get:
Simplify sinxcos(^3)x - cosxsin(^3)x by espressing it in the form of asin(bx), where a and b are rational numbers...

could anyone help....????

 

[paddy@2011]

sin(x)*cos(x)^3-cos(x)*sin(x)^3
=sin(x)cos(x)[cos(x)^2-sin(x)^2]
=1/2*sin(2x)*cos(2x)
=1/4*sin(4x)


cheers

 

[karen88]

thnx so much

 

[karen88]

another question...

sorry... i feel so stupid.... but here's another question i dun get...

solve 2tan^3x + 7tan^2x + 2tanx -3=0 for 0 <= x <= 360 degrees to nearest min

 

[Captain pi]

Expand tan(3x) and tan(2x) such that you have a polynomial in tan(x).

Go from there.

 

[karen88]

its not tan3x and tan2x... its tan cubed x and tan squared x... the ^ means that its power of

 

[shafqat]

let y = tan x to make it into a poly in y
2y^3 + 7y^2 + 2y - 3 = 0
factorising, (y+1)(2y-1)(y+3) = 0
so tan x = -1, 1/2, -3
u can do the rest