Trigonometric Identities

[nycmathguy]

Section 4.3

 

[MathLover1]

correction to wrong one
50.

sin^2(θ)-cos^2(θ)=2sin^2(θ)-1

use identity cos^2(theta)=1-sin^2(theta)

sin^2(θ)-(1-sin^2(theta))=2sin^2(θ)-1

sin^2(θ)-1+sin^2(theta)=2sin^2(θ)-1

2sin^2(θ)-1=2sin^2(θ)-1

 

[nycmathguy]

correction to wrong one
50.

sin^2(θ)-cos^2(θ)=2sin^2(θ)-1

use identity cos^2(theta)=1-sin^2(theta)

sin^2(θ)-(1-sin^2(theta))=2sin^2(θ)-1

sin^2(θ)-1+sin^2(theta)=2sin^2(θ)-1

2sin^2(θ)-1=2sin^2(θ)-1

Thanks. I like proving trigonometric Identities. It's a fun math exercise.