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Find the tangent to curve y=2cot(3x)-3cosec(4x) when x =pi/6

I’m going back and fourth with myself in my because my working out seems far too long….

So, the gradient I got is

F’(x) = 12cosec(4x)cot(4x)-6cosec^2(3x)

At x=pi/6

F’(pi/6)=12cosec(2pi/3)cot(2pi/3)-6cosec^2(pi/2)


The y coordinate for the tangent is:

2cot(pi/2)-3cosec(2pi/3) when x =pi/6


The answer asks for in exact form….

Am I meant to leave it such form as above? Or would I simply y to root form : -2root3 as 2cot(pi/2) is invalid
Reply 1
Original post by KingRich
I’m going back and fourth with myself in my because my working out seems far too long….

So, the gradient I got is

F’(x) = 12cosec(4x)cot(4x)-6cosec^2(3x)

At x=pi/6

F’(pi/6)=12cosec(2pi/3)cot(2pi/3)-6cosec^2(pi/2)


The y coordinate for the tangent is:

2cot(pi/2)-3cosec(2pi/3) when x =pi/6


The answer asks for in exact form….

Am I meant to leave it such form as above? Or would I simply y to root form : -2root3 as 2cot(pi/2) is invalid

derivative looks ok, if its in exact form theyd want the surd values of the trig terms and it written as the equation of a line.
cot(pi/2) is not invalid. tan(pi/2) is undeffined.
(edited 4 months ago)
Reply 2
Sorry, I mean undefined. What’s the difference? Just so I know in layman’s terms lol.


Yeah, I finally got there in the end y=-14x+7pi/3-2root3

I had trouble with this one but I’ve been full of flu, so I assume it’s because of that
Reply 3
Original post by KingRich
Sorry, I mean undefined. What’s the difference? Just so I know in layman’s terms lol.


Yeah, I finally got there in the end y=-14x+7pi/3-2root3

I had trouble with this one but I’ve been full of flu, so I assume it’s because of that

tan(pi/2) is undefined as its sin(pi/2)/cos(pi/2) = 1/0
cot(pi/2) is cos(pi/2)/sin(pi/2) = ....
So cot(pi/2) has a value. Again a sketch of the curves should make it clear

Whether you say tan(pi/2) is invalid or undefined isnt hugely important at a level. However, saying cot(pi/2) is invalid or undefined is wrong.
(edited 4 months ago)

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