farmer1

find all values of x from -pie<x<pie

of this equation

tanx=cosx

this is what i have got so far:

tanx=cosx
=>sinx/cosx=cosx
=>sinx=cos^2x
=>sinx=1-sin^2x
=>sin^2x+sinx-1=0

This is were i would like to factorise it but because of the difference in two squares it won't, so what do I do????

davegtt

u expect us to work that out at 4:45 on a friday afternoon? your avin a giraffe

RichWalk

well lets see, you have a tank, a pie, a sink, a sin and a cosie........

find a motor sport bod, ask him to fit your cosie engine in the tank, then bribe him with his sin full desire of pies, to make sure its doesnt sink.

How have I done???

O-level maths i got, knew it would come in handy one day

farmer1

I have been doing this all day since 10am bar an hour break for lunch

Sprint Chief

Your quadratic can be solved in the usual way

Substitute u=sin x

Quadratic is u^2 + u - 1 = 0

Solve for u = (-b +/- sqrt(b^2-4ac) / 2a
a = 1, b = 1, c = -1

u = (-1 +/- sqrt(5)) / 2

... which has two roots, u=0.6180 and u=-1.6180

x = arcsin u

which means (approx)

x = 0.6662
x = 1.5708 + 1.0613i

farmer1

Cheers for that I did try using the formula but was putting sin in instead of 1 etc. Didn't think of substituting, its been a long day.

Thanks for your help.

fast bloke

farmer - have you considered changing subjects? you gonna struggle big time with the exam unless you can bring a PC, and internet connection, ajm and Sprint Chief with you