A2: Asmt#2: Area of a trapezoid

Write a C program to do the following.

Write a C program that takes as input the values for x1 and x2, where x2 is greater than x1, and then the values y1 and y2 as the height above x1 and x2, respectively, and outputs the area of the trapezoid specified by those points. If the requirements are unclear in any way, use any provided input and output to resolve the discrepancy.

See Guidelines for C programs .

Domain knowledge is the background knowledge that is useful in solving a problem, designing a solution, implementing the solution, etc. The following domain knowledge may be useful for this requirement.

Area of a trapezoid

Note: In addition to specific domain knowledge, you should be familiar with all concepts covered to this point in the course.

A program should do what is requested, no more and no less. Since you are told that x2 is always greater than x1 there should be no check to see if that is true. That is the responsibility of some outer code or data (or the user when doing manual input).

Note that points are always represented as follows.

( x-value , y-value )

The following coding examples and/or notes may be of use for this requirement.

Area of a square

Make all necessary assumptions. Make no unnecessary assumptions.

In addition to specific coding examples, you should be familiar with all concepts covered to this point in the course.

You are provided with the following starter program in file traparea.c.

Do not remove any comment that starts with three slashes.

Here is the C code.

/// File: traparea.c
/// Purpose: Area of a trapezoid
/// Author: (your name)
/// Help received:
// (add here)
/// pseudo-code:
// (add here)

#include <stdio.h>

int main() {
	///:BEGIN ToDo

	///:END ToDo
	return 0;
	}

You are to fill in the missing parts of the program according to the work requirements (see above).

In the comments at the top, you are to fill in the author (your name), help received (person and type of help), and pseudo-code parts which are not in the solution (usually provided, but you need to add them). Remove the parentheses too.

Begin solution

Here is a possible solution to the above problem. Note: Once a solution is provided, or the day before the next class, further submissions for this work receive no credit.

/// File: traparea.c
/// Purpose: Area of a trapezoid
/// Author: (your name)
/// Help received:
// (add here)
/// pseudo-code:
// (add here)

#include <stdio.h>

int main() {
	///:BEGIN ToDo
	// declarations
	double x1,x2,y1,y2,area1;
	double y0 = 0.0;
	// input
	printf("Enter x1 and x2.\n");
	scanf("%lf %lf",&x1,&x2);
	printf("You entered x1 as %0.2lf and x2 as %0.2lf.\n",x1,x2);
	printf("Enter y1 and y2.\n");
	scanf("%lf %lf",&y1,&y2);
	printf("You entered y1 as %0.2lf and y2 as %0.2lf.\n",y1,y2);
	// process
	area1 = (x2 - x1) * 0.5 * (y1 + y2);
	// output
	printf("\n");
	printf("From the lower-left point clockwise,\n");
	printf("the points of the trapezoid are:\n");
	printf("\t(%0.2lf, %0.2lf)\n",x1,y0);
	printf("\t(%0.2lf, %0.2lf)\n",x1,y1);
	printf("\t(%0.2lf, %0.2lf)\n",x2,y2);
	printf("\t(%0.2lf, %0.2lf)\n",x2,y0);
	printf("The area of the trapezoid is %0.2lf units.\n",area1);
	///:END ToDo
	return 0;
	}

End solution

Here are some examples of input and output for the above program code.

Here is an example input from file input1.txt.

1.0 2.0
1.0 1.0

For the above example input, here is the expected output.

Enter x1 and x2.
You entered x1 as 1.00 and x2 as 2.00.
Enter y1 and y2.
You entered y1 as 1.00 and y2 as 1.00.

From the lower-left point clockwise,
the points of the trapezoid are:
	(1.00, 0.00)
	(1.00, 1.00)
	(2.00, 1.00)
	(2.00, 0.00)
The area of the trapezoid is 1.00 units.

Here is an example input from file input2.txt.

3.3 4.4
1.1 2.2

For the above example input, here is the expected output.

Enter x1 and x2.
You entered x1 as 3.30 and x2 as 4.40.
Enter y1 and y2.
You entered y1 as 1.10 and y2 as 2.20.

From the lower-left point clockwise,
the points of the trapezoid are:
	(3.30, 0.00)
	(3.30, 1.10)
	(4.40, 2.20)
	(4.40, 0.00)
The area of the trapezoid is 1.82 units.

Here is an example input from file input3.txt.

5.1 8.3
12.2 8.4

For the above example input, here is the expected output.

Enter x1 and x2.
You entered x1 as 5.10 and x2 as 8.30.
Enter y1 and y2.
You entered y1 as 12.20 and y2 as 8.40.

From the lower-left point clockwise,
the points of the trapezoid are:
	(5.10, 0.00)
	(5.10, 12.20)
	(8.30, 8.40)
	(8.30, 0.00)
The area of the trapezoid is 32.96 units.

Pseudo-code is a "false" code. It is not really code, but a simplified English explanation that is somewhat similar to code. Pseudo-code is useful for understanding what a program does. For this work, the following can be used as the pseudo-code. Adjust if needed.

Get points of the trapezoid
Compute area of the trapezoid
Output points and area of trapezad.

Note: Only some essential details are included. Some details, such as input, prompts, input echo, and obviously needed output are omitted.

The best way to copy-paste pseudo-code that includes indented code (e.g., with tabs) is as follows (in the code file) using a multi-line comment.

/* (pasted pseudo-code here) */

CS 101 - A2 : Asmt#2: Area of a trapezoid Your grade: _ / 40 [LATE] Late or redo penalty: _ / -40 [SUBMIT] Not submitted properly: _ / -40 [RUN] Does not compile, run-time crash, etc.: _ / -40 [ETHICS] Ethical issues: _ / -40 [HEADER] Header comments not done as required: _ / -20 [STYLE] Inconsistant style or indentation: _ / -20 [CODE] Code guidelines ignored: _ / -40 [XCODE] Code used not yet covered: _ / -20 [REMOVED] Triple slash comments removed: _ / -20 [ADDED] Code added outside of marked areas: _ / -20 [OUTPUT] Functional requirements met: _ / 40 [CREDIT] Extra credit: _ / +8 Comments: