What value of theta maximizes the area of a triangle with sides a and b?

In summary, the question asks for the value of theta that will maximize the area of a triangle with sides a and b. The solution involves taking the derivative of the area function with respect to theta, which results in cos(theta) = 0. This gives an angle of pi, which corresponds to a right triangle, making sense since right triangles have the greatest area.
  • #1
cheezeitz
8
0

Homework Statement


Two sides of a triangle have lengths a and b, and the angle between them is theta. What value of theta will maximize the triangle's area? (Hint: A=1/2absin(theta)



The Attempt at a Solution


I have a triangle drawn, with the base being a, and the height being b. From the equation given, does the value of b actually equal theta times the angle?
I'm trying to relate the two angles so i can solve for one variable, but not sure where to start.
 
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  • #2
Ok, well it seems like you are trying to say one leg of the triangle is the height. But look at the hint. A=1/2 b*h if you anchor one leg on an axis, then let the other leg move
You have a base b, and the h=asin(theta) Anyway, if you take dA/dtheta that's how the area changes as theta changes. So basically just take the derivative of that area function with respect to theta. When that function equals 0, you have a maximum area.

I tried it out, and you end up with 1/2(absin(theta)) a and b are constant so dA/dtheta = 1/2(abcos(theta) Set that equal to 0. divide out the constants, you have cos(theta) = 0

This gives you an angle of pi, which would be a right triangle, which makes sense to me. Shouldn't the right triangle have the greatest area?

Hope that makes sense.
 

Related to What value of theta maximizes the area of a triangle with sides a and b?

What is the definition of a derivative?

A derivative is a mathematical tool used to measure the rate of change of a function at a specific point. It is calculated as the slope of a tangent line to the curve of the function at that point.

What are the main applications of derivatives?

Derivatives are used in a wide range of fields, including physics, economics, engineering, and more. Some of the main applications include optimization, finding maximum and minimum values, and determining rates of change.

How is the chain rule used in the application of derivatives?

The chain rule is a method for finding the derivative of a composite function, which is a function that is made up of two or more other functions. It is a crucial tool in the application of derivatives as it allows us to find the derivative of more complex functions.

What is the difference between a local and global extremum?

A local extremum is a point on a curve where the function reaches a maximum or minimum value, but only in a certain interval or region. A global extremum is a point where the function reaches the maximum or minimum value over its entire domain.

What is the relationship between derivatives and the shape of a graph?

Derivatives can give us information about the shape of a graph, such as whether the curve is increasing or decreasing, or whether it has a concave up or concave down shape. They can also help us identify critical points, where the slope of the tangent line is zero, and determine whether they are maximum or minimum points.

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