CSCI 261 - Programming Concepts (C++)

Spring 2018 - Assignment 2 - Random Triangles

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This assignment is due by Tuesday, January 30, 2017 11:59 PM.

As you will learn, we LOVE triangles in this class. (And I particularly love them in the computer graphics class). Get ready to learn more than you'll ever want to about geometry and triangles.

Instructions: Part I - Classify Their Triangle

Write code to first read three real value measurements, i.e., your program should prompt the user to enter the three real values (which should be stored as three double variables). Once done, write code to determine whether the three real value measurements make a triangle. If yes, your program should tell the user whether the triangle is a right, acute, or obtuse triangle (see hints below). If no, your program should politely terminate with an appropriate error message.

The user should be allowed to enter the three real values in any order; in other words, your program should not assume any particular input order such as ascending or descending.

Hints

A triangle is possible IFF each side is smaller than the sum of the others.
To classify a triangle, first you need to determine which of the three sides is the longest. The variable names a, b, and c are often used for the sides of a triangle, with c being the longest. If c is the longest side of the triangle, then the triangle is a right triangle if (and only if) a² + b² == c².
Due to the imprecise nature of double variables, you cannot directly compare two double variables with the == operator. Instead, you should do the comparison using a TOLERANCE constant (e.g., TOLERANCE == 0.0001) in the following way:

// The fabs function (defined in cmath) returns the absolute value of a given floating point number.
// Thus, if the following equation is true, then we assume a² + b² == c².
fabs(a² + b² - c²) <= TOLERANCE

The TOLERANCE constant represents the error we are willing to accept when comparing two double values for equality; in other words, if two values are different by TOLERANCE (or less), then we consider the two values as equivalent. In your program, declare a TOLERANCE constant and set it to 0.0001.
You must check to see if the triangle is a right triangle first; otherwise you may be classifying a right triangle as acute or obtuse by mistake.
If the triangle is not right, you should then check whether if it is acute (i.e., a² + b² > c²).
Otherwise, if the triangle is not right or acute, then you can say the triangle is obtuse (i.e., a² + b² < c²)

Test Values

Here are some known input/output values that you can test against. Be sure to try your own to verify the code works!

Inputs	Classification	Purpose of Test
3 4 5	Right	Known Right Triangle
5 12 13	Right	Known Right Triangle
5 5 9	Obtuse	Known Obtuse Triangle
5 5 1	Acute	Known Acute Triangle Sides are not in increasing order Two sides share the longest length
1 1 1	Acute	Known Acute Triange All sides share the longest length
1 2 3	Not a Triangle	Invalid triangle. `a + b > c` fails
3 4 0	Not a Triangle	Invalid triangle. One side has a zero length
-3 -4 -5	Not a Triangle	Invalid triangle. All sides have negative lengths (even though `a² + b² = c²` would still hold.)

Instructions: Part II - Triangle Stats

If the result of Part I determines we do have a valid triangle, then we will continue to print out some stats about our triangle. We first will want to print out the three sides in increasing order. Then, we will print out both the perimeter and area of the triangle.

Hints

Perhaps there is an easy way to compute the area knowing only the side lengths...

Test Values

Here are some known input/output values that you can test against. Be sure to try your own to verify the code works!

Inputs	Classification	Perimeter	Area	Purpose of Test
3 5 4	Right	12	6	Known Right Triangle Sides are not in increasing order
13 12 5	Right	30	30	Known Right Triangle Sides are not in increasing order
5 5 9	Obtuse	19	9.8075	Known Obtuse Triangle
5 5 1	Acute	11	2.4875	Known Acute Triangle Sides are not in increasing order Two sides share the longest length
1 1 1	Acute	3	0.433	Known Acute Triangle All sides share the longest length
1 2 3	Not a Triangle			Invalid triangle. `a + b > c` fails
3 4 0	Not a Triangle			Invalid triangle. One side has a zero length
-3 -4 -5	Not a Triangle			Invalid triangle. All sides have negative lengths (even though `a² + b² = c²` would still hold.)

Instructions: Part III - Randomize The Triangle

Now for the tricky part. We are going to go back and edit what we did at the very beginning. Initially, the user was entering the length of the three sides. Instead, we want to ask the user to enter the first two sides of a triangle. We then need our program to generate a third random real side length that results in a valid triangle. Given the hints above, what can the minimum and maximum possible values be? The rest of the program will then proceed as before using the randomly generated value.

Grading Rubric

Your submission will be graded according to the following rubric.

Points	Requirement Description
2	All code submitted properly
10	Labs completed
+2	Lab 2E Extra Credit
2	In-class exercises completed
5	Triangle side length computed as random floating point values
6	Triangle properly classified
4	Triangle stats printed properly
2	(1) Comments used (2) Coding style followed (3) Appropriate variable names, constants, and data types used (4) Instructions followed
31	Total Points

Submission

Always, always, ALWAYS update the header comments at the top of your main.cpp file. And if you ever get stuck, remember that there is LOTS of help available.

From your Cloud9 workspace, right click on the Set2 folder in your workspace tree. Select "Download" from the pop-up menu. This will download a file called Set2.zip to your computer. It contains all the files of your Set2 folder (therefore L2A, L2B, L2C, L2D, L2E, A2).

Now in Canvas, go to Assignments > Set2. Upload your Set2.zip file you just downloaded. And voila! Easy peasy.

In summary, follow these specific steps:

right click on the Set2 folder in Cloud9.
select "Download" from the pop-up menu.
upload the Set2.zip file to Canvas Set2.
after you submit, download the file and double check it contains all that you think it contains!

This assignment is due by Tuesday, January 30, 2017 11:59 PM.

Last Updated: 01/08/18 15:57

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