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Mathematics
OpenStudy (anonymous):

An equation of the line tangent to the graph of y=cos(2x) at x=π/4 is? Help please?

hero (hero):

Do you have a graphing calculator?

OpenStudy (anonymous):

yes i do

hero (hero):

Hold on for a minute

OpenStudy (anonymous):

okay

hero (hero):

There is a formula for this

OpenStudy (anonymous):

and i have no clue what it is?

hero (hero):

Sorry, it's called Linear Approximation

hero (hero):

y - f(c) = f'(c)(x - c)

hero (hero):

y - f(pi/4) = f'(pi/4)(x - pi/4)

hero (hero):

If you evaluate that, you'll get your answer

OpenStudy (anonymous):

ohhh okay... i knew there was a formula but i didn't know which one... that helps me out a lot thanks so much!

hero (hero):

Make sure if you're using a calculator that you're in radians, not degrees

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