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MermaidWonders
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True or False: If $$h(t) > 0$$ for $$0 \le t\le 1$$, then the function $$H(x) = \int_{0}^{x} h(t)\,dt$$ is concave up for $$0 \le t\le 1$$.
MermaidWonders said:Like where a function's second derivative is > 0?
MermaidWonders said:Wait, so how do I get the sign of $H''(x)$? From the question, I know that since the fundamental theorem tells me that $H'(x)$ = $h(x)$, and that $h(t) > 0$, $H'(x)$ will also be $< 0$. But how do I figure out the concavity from there?
I like Serena said:Indeed. So we know that $H'(x)>0$ (positive not negative) for $0\le x \le 1$, but we still don't know anything about $H''(x)$.
We can only tell that $H$ is strictly increasing and that it is strictly positive on the interval. We cannot say if it's convex or concave.
MarkFL said:Indeed, and is why I resorted to looking for a function satisfying the given criteria, that is not concave up on the given interval. :)
I like Serena said:Unfortunately, with $h(t)=c$, the function $H$ is actually concave up ($H''(x)\ge 0$), just not strictly concave up.
But yes, it does illustrate that we cannot just make the function (strictly) concave up.
MermaidWonders said:Ah, so if we don't know if it's concave up or concave down, the statement is false?
MermaidWonders said:Wait, I'm still confused. Can anyone give me like an overall explanation/walkthrough to get to this conclusion? I really want to make sure I understand it. :(
MarkFL said:Perhaps there are differences in terminology...I was taught that a function is concave up on an interval when its second derivative is positive, and concave down when its second derivative is negative. When the derivative of a function is constant, then the function itself has no concavity.
MermaidWonders said:Wait, I'm still confused. Can anyone give me like an overall explanation/walkthrough to get to this conclusion? I really want to make sure I understand it. :(
I like Serena said:I can only refer to the wiki page, which is consistent with what I've learned. And I've never heard or seen that it could be different. Can you perhaps provide a reference?
MarkFL said:I was simply taught that a linear function has no concavity...just recalling from memory. :)
Integral calculus is a branch of mathematics that deals with finding the area under a curve. It is used to solve problems involving continuous change, such as finding the velocity of an object or the volume of a 3D shape.
The difference between true and false integral calculus lies in the concept of integration. In true integral calculus, the limits of integration are fixed and definite, while in false integral calculus, the limits are variable and indefinite. This leads to different methods and results in solving problems.
To determine if an integral is true or false, you need to check the limits of integration. If they are fixed and definite, then it is a true integral. If the limits are variable and indefinite, then it is a false integral.
Integral calculus has various real-world applications, such as in physics, engineering, economics, and statistics. For example, it can be used to calculate the work done by a force or the total profit of a business. It is also used in optimization problems to find the maximum or minimum value of a function.
Some common techniques for solving true or false integral calculus problems include substitution, integration by parts, trigonometric substitution, and partial fractions. These techniques involve manipulating the integrand and using known integration rules to solve the integral.