Homework Q&A

Tools

Home > Trigonometry > Proving Identities

Cos (pi + x) + cos (pi-x) ?

Answer 1

Carter Anderson

Carter Anderson

#color (blue)(-2cos x)#

We have #Cos (pi + x) + cos (pi-x)#

Identities that we are going to use are as follows #color (red)(cos (a+b)=cos a cos b-sin a sin b)# And

#color (red)(cos (a-b)=cos a cos b+sin a sin b)#

It is quite clear that #cos (a-b)+cos (a+b)=2cos a cos b#

Plugging in values for a and b, we get #Cos (pi + x) + cos (pi-x)=2cos pi cos x=-2cos x# {Note:#cos pi=-1#}

Sign up to view the whole answer

By signing up, you agree to our Terms of Service and Privacy Policy

Sign up with email

Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

Trending questions

Not the question you need?

Answer Background

HIX Tutor

Solve ANY homework problem with a smart AI

98% accuracy study help
Covers math, physics, chemistry, biology, and more
Step-by-step, in-depth guides
Readily available 24/7