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Mathematics 18 Online
OpenStudy (anonymous):

verify each identity

OpenStudy (anonymous):

Whats the question

OpenStudy (anonymous):

k

OpenStudy (anonymous):

jhonyy9 (jhonyy9):

do you know what mean csc x ?

jhonyy9 (jhonyy9):

so csc x = ? and how can you rewriting cot x and tan x using sin x and cos x ?

OpenStudy (anonymous):

@mathstudent55

OpenStudy (anonymous):

ITS NUMBER 2 IN THE PICTURE

OpenStudy (mathstudent55):

\(\sin (x + \pi) = -\sin x\)

OpenStudy (anonymous):

yes i got that part do you want to see my work?

OpenStudy (mathstudent55):

No, I don't see your work. i only see the question in the figure.

OpenStudy (anonymous):

OpenStudy (mathstudent55):

Ok, let's take it from the beginning. \(\Large \dfrac{\sin (x + \pi)}{\cos (x + \frac{3\pi}{2})} = \tan^2 x - \sec^2 x\)

OpenStudy (anonymous):

that's my work

OpenStudy (mathstudent55):

We use the identity for sin & cos of sums: \(\Large \dfrac{\sin x \cos \pi + \sin \pi \cos x}{\cos x \cos \frac{3\pi}{2} - \sin x \sin \frac{3\pi}{2}} = \tan^2 x - \sec^2 x\)

OpenStudy (mathstudent55):

I see your work now. So far we have exactly the same.

OpenStudy (mathstudent55):

Now let's take the sin & cos of pi and 3pi/2

OpenStudy (anonymous):

did i get that part right?

OpenStudy (mathstudent55):

\(\Large \dfrac{(\sin x )(-1) + (0) \cos x}{(\cos x)(0) - (\sin x)(-1)} = \tan^2 x - \sec^2 x\)

OpenStudy (mathstudent55):

You are very close, but I think you have a 1 where it should be -1 as the sin 3pi/2 at the end of the denominator.

OpenStudy (anonymous):

what is sin of 3pi/2?

OpenStudy (anonymous):

is it 1?

OpenStudy (mathstudent55):

\(\Large \dfrac{-\sin x }{\sin x} = \tan^2 x - \sec^2 x\)

OpenStudy (mathstudent55):

sin 3pi/2 = -1

OpenStudy (anonymous):

HOW DID YOU FIND THE OUT?

OpenStudy (anonymous):

since it's -1 wouldnt be postive because it's 0-sin(-1) = 0+sin(1)

OpenStudy (mathstudent55):

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