Helen's Holiday Blog #3

8-5

• You would use the identities to get to the same trig function. If you can't try to make it tan or cot by sin/cos or cos/sin
• Follow the inverse rules

Things you CAN'T do!!!!!!!!!!!

1. Divide by a trig function when solving to cancel.

2.Cancel from the inside of a trig function.

Ex: sin(2x)/2 = you CAN'T cancel the 2

Examples:

1)2sin^2 theta-1=0
2sin^2 theta=1
sin^2 theta=1/2
sin theta = +/- sq.root of 1/2
theta= sin inverse (sq. root of 1/2)


2)sin^2x-sinx=cos^2 x
sin^2x-sinx=1-sin^2x
2sin^2x-sinx-1=0

(2sin^2 x -2sinx)+(sinx-1)=0
2sinx(sinx-1)+(sinx-1)=0
(2sinx+1)(sinx-1)=0

2sinx+1=0 sinx-1=0
sinx=-1/2 sinx=1
x=sin inverse (1/2) x=sin inverse (1)

x=7π/6,11π/6,π/2 x=π/2

3)sinxtanx=3sinx
sinxtanx-3sinx=0
sinx(tanx-3)=0

sinx=0 tanx-3=0
x=sin inverse(0) x=tan inverse (3)


Answer: 0,71.565,180,251.565,360