Helen's Blog #4?

I'll be showing you what I learned on section 8-1 and 8-2.

8-1 ( Solving for Theta)

1: To solve for theta you get the function by itself, then you take the inverse.

2: An inverse has 2 answers with some exceptions, Find where the angle is based on trig function and it the number is positive or negative.

3: Steps to take the inverse of the positive number to find the quadrant angle.

STEPS:

To get to :
Q2: Make negative, then add 180°
Q3: Add 180°
Q4: Make negative, then add 360°

Example:

3 Cos(theta) + 9=7

1: You would have to subtract 9 on the other side.
3Cos(theta)= -2

2: You would divide 3 on the other side.
Cos(theta)=-2/3

3: You would have to get the inverse cosine of -2/3.
theta=Cos^{−1(-2/3)
= 48.1897}°

4: Moving to QII & QIII
QII: Make negative, then add 180°( -48.1897+180= 131.810°)

QIII: Add 180° ( 48.1897+180= 228.190°)

Answer : 131.810°,228.190°

8-2

To Graph with a Period Change

• y= A sin Bx or y= A cos Bx

• |a|= Amplitude
• 2/ B= Period
  

STEPS:

1: Take all 5 points
2: Divide by B.
3: Sketch

Example:

y=2 sin 2x

Amp: 2
Period: 2/2=

1: 0 0/2=0
2:/2 *1/2=/4
3:/2
4:3/2 * 1/2=3/4
5:2/2=

Last you would graph it.