Trig identities

[User9**7]

Is cos²x equal to -cos²x ?

 

[Deleted member 4993]

Is cos²x equal to -cos²x ?

Not in general.

However, there are situations where the stated functions will have the same value.

 

[JeffM]

[MATH]r = - r \implies r = \text {WHAT?}[/MATH]
[MATH]\therefore q^2 = - q^2 \implies q^2 = \text {WHAT?} \implies q = \text {WHAT?}[/MATH]
What does that tell you about [MATH]cos^2(x) = - cos^2(x)?[/MATH]

 

[Steven G]

If cos²x = -cos²x, then 2cos²x=0. Then cos²x=?. Then cosx = ? Does cos x always equal the same value?