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Given the graph, we want to find the equation for the tangent to
the curve at P where P is π halves, one, so I found the one.
Apparently I didn't need to do that if I'd looked at the graph.
I went by the equation Y equal 3 plus cotangent X -, 2 cosec and
XI stuck in Pi halves everywhere and I got Y of π halves equaling
one which was given in the graph.
So now we needed Y prime so we can find the slope of this line.
So I take the derivative of the given equation and I get
negative cosecant squared X + 2 cosecant X cotangent X sticking
in Pi halves and knowing my unit circle negative cosecant squared
Pi halves.
Well, cosecant Pi halves is one and 1 * 1 is 1 + 2.
Cosecant Pi halves is one.
Again, cotangent Pi halves is 0, so our slope here is -1 using
point slope form y -, 1 equal -1 times the quantity X - π halves.
Distributing out the -1 and adding the -1 that was on the
left side over to the right, we get Y equal negative X + π
halves plus one.
Now the second part says the horizontal tangent to the curve
at Q.
So if it's a horizontal tangent, we know the first derivative has
to equal 0.
So I'm going to take that first derivative, set it equal to 0
and a factor out of cosecant X.
So I know that cosecant X = 0 and also negative cosecant X +
2, cotangent X = 0.
Well, cosecant X is never zero.
It has to be in between negative Infinity and -1 and one to
Infinity.
So cosec an X is never 0.
So looking at the second one negative cosec an X + 2
cotangent X = 0.
I'm going to add the cosec an X across and I realized that I get
2 cosec an X over sine X equaling one over sine X.
So I'm going to multiply each side by sine X, making sure to
recall in the end that sine X can't equal 0 if I get an angle
that would have it as that.
So we get 2 cosine X equal 1.
Cosine X is 1/2.
Knowing my unit circle, I know that cosine X is 1/2 at π thirds
also at 5 Pi thirds.
But when we look at the graph, we can see that Q is less than
P&P was Pi halves.
So we're wanting the π thirds location.
So now to get the actual height, we're going to put that π thirds
into the original equation.
Y = 3 plus cotangent π thirds -2 cosecant π thirds, cotangent Π
thirds by knowing our unit circle is root 3 / 3 cosecant π
thirds.
Once again knowing our unit circle is 2 root 3 / 3, so we
get the three and root 3 / 3 - 4.
Root 3 is over three, so 1 -, 4 is -3 Root 3 is over three or
just negative root 3.