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# Differentiation question (trig)

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1. Would the Dy/DX of Sec squared 3x be 3 Sec sqaured 3x 3Tan Squared 3x
2. (Original post by SunDun111)
Would the Dy/DX of Sec squared 3x be 3 Sec sqaured 3x 3Tan Squared 3x
It would be 6tan(3x)sec^2(3x)
3. (Original post by SunDun111)
Would the Dy/DX of Sec squared 3x be 3 Sec sqaured 3x 3Tan Squared 3x
No, why do you think that?

and
4. (Original post by jjsnyder)
It would be 2(3secxtanx)^2
Are you sure?
5. (Original post by Zacken)
No, why do you think that?

and
Because my teacher didnt teach us the DY/DX of Cot, Cosec and Sec so I am going over it. I thought it would be a 3 Tan 3x but I get it now thank you!
6. (Original post by Zacken)
Are you sure?
Aha no totally misread the question :P
7. (Original post by SunDun111)
Because my teacher didnt teach us the DY/DX of Cot, Cosec and Sec so I am going over it. I thought it would be a 3 Tan 3x but I get it now thank you!
Just rewrite and then use the chain rule. Same applies for the other two reciprocal functions.
8. (Original post by SunDun111)
Because my teacher didnt teach us the DY/DX of Cot, Cosec and Sec so I am going over it. I thought it would be a 3 Tan 3x but I get it now thank you!
they are just reciprocal of tan, sin and cos so just differentiate them in the tan/sin/cos form.

Edit: whooops
9. (Original post by Zacken)
Just rewrite and then use the chain rule. Same applies for the other two reciprocal functions.
Quick question, once I differentiate a trig function, it asks me to show it is an increasing function? What do I do.
10. (Original post by SunDun111)
Quick question, once I differentiate a trig function, it asks me to show it is an increasing function? What do I do.
A function is increasing if its derivative for all .

So can you show that your derivative is always positive? Maybe it's a squared quantity or something.
11. (Original post by Zacken)
A function is increasing if its derivative for all .

So can you show that your derivative is always positive? Maybe it's a squared quantity or something.
Well its 2Sec2x Tan2x + 2Sec Squared 2x
12. (Original post by SunDun111)
Well its 2Sec2x Tan2x + 2Sec Squared 2x
What's the original function?
13. (Original post by Zacken)
What's the original function?
The original function was Sec 2x + Tan 2x I had to Differentiate it, it was defined by -pi/4 < x < pi/4
14. (Original post by SunDun111)
The original function was Sec 2x + Tan 2x I had to Differentiate it, it was defined by -pi/4 < x < pi/4
Okay, so that got you as your rightly said. Can you show that that is always positive (for the given interval of x, obviously).

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