trig mk9

Same value of x as last 2 threads i made

tanx=cosx

sinx=cos²x

sinx=1-sin²x

sin²x+sinx-1=0

let sinx=y

y²+y-1=0

quaratic equation gives me (-1±root 2)/2

then i got a wrong answer >.>
help, where have i made a stupid mistake this time

@TeeEm @Zacken

Reply 1

TeeEm

19

Original post by thefatone

Same value of x as last 2 threads i made

tanx=cosx

sinx=cos²x

sinx=1-sin²x

sin²x+sinx-1=0

let sinx=y

y²+y-1=0

quaratic equation gives me (-1±root 2)/2

then i got a wrong answer >.>
help, where have i made a stupid mistake this time

@TeeEm @Zacken

sorry I am teaching

Reply 2

thefatone

OP

6

Original post by TeeEm

sorry I am teaching

oh.. ok

Reply 3

Bath_Student

3

Original post by thefatone

Same value of x as last 2 threads i made

tanx=cosx

sinx=cos²x

sinx=1-sin²x

sin²x+sinx-1=0

let sinx=y

y²+y-1=0

quaratic equation gives me (-1±root 2)/2

then i got a wrong answer >.>
help, where have i made a stupid mistake this time

@TeeEm @Zacken

There's where.

Reply 4

Zacken

22

Original post by thefatone

Same value of x as last 2 threads i made

tanx=cosx

sinx=cos²x

sinx=1-sin²x

sin²x+sinx-1=0

let sinx=y

y²+y-1=0

quaratic equation gives me (-1±root 2)/2

then i got a wrong answer >.>
help, where have i made a stupid mistake this time

@TeeEm @Zacken

As above, solving the quadratic equation gives: