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Mathematics 18 Online
OpenStudy (anonymous):

Does sin(x)+sin(x)cot(x)=csc(x)

OpenStudy (freckles):

let's find out first notice you can factor the left hand side

OpenStudy (freckles):

also is there suppose to be a square on cot?

OpenStudy (anonymous):

nope, there is no square, my teacher just wanted us to prove (or disprove) if the equation was equivalent or not.

OpenStudy (freckles):

did you try pluggin in a value to see if both sides are the same or not

OpenStudy (anonymous):

There was no value for x, I just put them there instead of the weird circle thingy that you use for cos sin and tan equations

OpenStudy (anonymous):

I makes more sence to me then I put them back in later

OpenStudy (freckles):

no like finding a counterexample by choosing a value of x such that both sides are different

OpenStudy (freckles):

for example choose x =pi/6

OpenStudy (freckles):

are both side the same ?

OpenStudy (freckles):

\[\sin(\frac{\pi}{6})+\sin(\frac{\pi}{6}) \cot(\frac{\pi}{6})=? \\ \csc(\frac{\pi}{6})=?\]

OpenStudy (anonymous):

Do I have to use values that I would find on the unit circle, or could I just plug in any number (ex 1 or 10, etc)

OpenStudy (freckles):

it doesn't matter what value of x you choose as long as it works to show the equation is false the counterexample just means you are showing both sides aren't for all values of x and therefore the equation is not an identity this is what you do if you believe the equation given is false

OpenStudy (freckles):

otherwise you might want to try to prove it if you don't have that belief

OpenStudy (anonymous):

oh okay I just plugged in the equation with x=1 and the sides didn't match, so this proves that the two sides are NOT the same correct

OpenStudy (freckles):

that is right if we tried to prove it we get sin(x)+sin(x)cot(x) sin(x)[1+cot(x)] and this doesn't seem to me giving us csc(x) however if it was sin(x)+sin(x)cot^2(x) sin(x)[1+cot^2(x)] sin(x)[csc^2(x)] sin(x)*1/sin^2(x) sin(x)/sin^2(x) 1/sin(x) csc(x) this would work

OpenStudy (freckles):

so again the equation you were given was not true since you were able to provide a counterexample... that example you chose was x=1

OpenStudy (anonymous):

awesome!!! Thanks a whole bunch!!

OpenStudy (freckles):

np

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