# Convert to Rectangular Form...7

Discussion in 'Geometry and Trigonometry' started by nycmathguy, Mar 19, 2022.

1. ### nycmathguy

Joined:
Jun 27, 2021
Messages:
5,386
422
Cam you get me started with 11 and 13 by providing the first 2 steps? I will then try solving the problems on my own.

nycmathguy, Mar 19, 2022
2. ### MathLover1

Joined:
Jun 27, 2021
Messages:
2,989
2,884
11.

r=3cos(2θ)

first apply the formula cos(2θ)=cos^2(θ)-sin^2(θ)
r= 3cos^2(θ)-3sin^2(θ)

then use
x=rcos(θ) and y=rsin(θ)

you continue

13.

r^2=8/(2-sin^2(θ))

From x=rcos(θ) and y=rsin(θ), we have that
cos(θ)= x/r
sin(θ)= y/r
tan(θ)= y/x
cot(θ)= x/y

The input becomes
r^2 =8/(2- y^2/r ^2)

you continue

MathLover1, Mar 19, 2022
nycmathguy likes this.
3. ### nycmathguy

Joined:
Jun 27, 2021
Messages:
5,386
422

nycmathguy, Mar 19, 2022
4. ### MathLover1

Joined:
Jun 27, 2021
Messages:
2,989
2,884
11. need to finish, answer cannot have r , only x and y

13. correct

MathLover1, Mar 19, 2022
nycmathguy likes this.
5. ### nycmathguy

Joined:
Jun 27, 2021
Messages:
5,386
422
Can you finish 11 for me? I can't further simplify.

nycmathguy, Mar 19, 2022
6. ### MathLover1

Joined:
Jun 27, 2021
Messages:
2,989
2,884
11.

substitute

........ both sides raise to power of 3

#### Attached Files:

File size:
1.6 KB
Views:
9
File size:
1.8 KB
Views:
8
MathLover1, Mar 19, 2022
nycmathguy likes this.

Joined:
Jun 27, 2021
Messages:
5,386