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evtldocha
5 months ago

As a reminder: The derivative of a function at a certain point x is the slope of the tangent to the function at the point in question P(x | f(x)) and it holds



In part c) the intersection point of the function with the y-axis is at x=0 (ie the origin) and therefore



(arctan is often known today as tan -1 because the inverse function of the tangent is often labeled this way on pocket calculators)

This should also make it clear what has to be solved in part d) : Find the x at which

applies (there are 2 solutions if the angle of inclination of the tangents is understood as the acute angle to the x-axis)

Sketch for c)

Sketch for d)

Halbrecht
5 months ago
Reply to  evtldocha

In d) I am not sure whether one should not name only one

Or as a question: Does the parabola not have a slope angle of 260°

evtldocha
5 months ago
Reply to  Halbrecht

Well, I understand that people mean the acute angle, which is why I use the phrase " if you… understand the acute angle to the x-axis," knowing that there are different interpretations. My understanding has always been that the angle on the right is -60°. Then the next person comes along and says: "We're only looking for angles between 0° and 180°," and I say, "Okay—the vertex angle is then +60°, or whatever, or something else." And since teachers sometimes have very specific ideas and preferences anyway, the person asking the question should choose what applies to their class.

Halbrecht
5 months ago

Where is the angle?
Slope is defined as the slope of the tangents at the points

Therefore the angle (drawn roughly) at x = 0

this