3.15. Activecode Exercises

Answer the following Activecode questions to assess what you have learned in this chapter.

Fix the errors in the code below so that it prints the area of a circle with radius 5. Use cmath functions to get an accurate value for pi.

#include <iostream> #include <cmath> using namespace std; void printArea(int r) { double pi = acos(1.0); double area = pi * r ^ 2; cout << area; } int main () { // DO NOT MODIFY ANYTHING BELOW THIS LINE cout << "Testing with radius = 5..." << endl; cout << " Your function had area = "; printArea(5); cout << endl; cout << " The correct solution has area = 78.5398" << endl; cout << "Testing with radius = 7.5..." << endl; cout << " Your function had area = "; printArea(7.5); cout << endl; cout << " The correct solution has area = 176.715"; }

Below is one way to fix the program. C++ doesn’t use the ^ operator for exponents. We can get the square of r by multiplying it by itself. We call the function with an argument of 5.

#include <iostream> #include <cmath> using namespace std; void printArea(double r) { double pi = acos(-1.0); double area = pi * r * r; cout << area; }

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Selecting from: functions_a2, functions_a2_pp

Fix the code below so that it prints 12 / 8 = 1.5.

#include <iostream> using namespace std; void divide (int a, int b) { cout << a / b; } int main () { int a = 8; int b = 12; // DO NOT MODIFY ANYTHING BELOW THIS LINE cout << b << " / " << a << " = "; divide (b, a); }

Below is one way to fix the program. It’s crucial that you input your arguments in the correct order so as to avoid a semantic error. Also, it’s important that you understand that when you divide two integers… you will get an integer as a result.

#include <iostream> using namespace std; void divide (double a, double b) { cout << a / b; } int main () { int a = 8; int b = 12; cout << b << " / " << a << " = "; divide (b, a); }

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Selecting from: functions_a4, functions_a4_pp

Finish the code below so that it prints “First Line”, a border, and “Second Line.” on three separate lines.

#include <iostream> using namespace std; void border () { cout << "------------" << endl; } int main () { // Write some code below to call the function appropriately }

Below is one way to complete the program.

#include <iostream> using namespace std; void border () { cout << "------------" << endl; } int main () { cout << "First Line." << endl; border(); cout << "Second Line." << endl; }

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Selecting from: functions_a6, functions_a6_pp

Write a function called gpaBoost that prints your GPA rounded up to the nearest point. If your GPA is already at the nearest point, there is no rounding. Be sure to include any necessary headers.

#include <iostream> #include <cmath> using namespace std; void gpaBoost () { } int main () { // DO NOT MODIFY ANYTHING BELOW THIS LINE cout << "Testing with GPA = 2.513..." << endl; cout << " Your solution rounded the GPA to "; gpaBoost(2.513); cout << endl; cout << " The correct solution rounds the GPA to 3.000" << endl; cout << "Testing with GPA = 4.000..." << endl; cout << " Your solution rounded the GPA to "; gpaBoost(4.000); cout << endl; cout << " The correct solution rounds the GPA to 4.000"; }

Below is one way to complete the program. I used the ceil function from the cmath library, but you could have solved this problem without using any functions from cmath.

#include <iostream> #include <cmath> using namespace std; void gpaBoost (double GPA) { int betterGPA = ceil(GPA); cout << betterGPA << ".000"; }

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Selecting from: functions_a8, functions_a8_pp

Write a function called tanD that prints the tangent of an angle given as a double in degrees. Use 3.14 for pi. Be sure to include any necessary headers.

#include <iostream> #include <cmath> using namespace std; void tanDegrees () { } int main () { // DO NOT MODIFY ANYTHING BELOW THIS LINE cout << "Testing with degrees = 45..." << endl; cout << " Your solution calculated a tangent of "; tanDegrees(45); cout << endl; cout << " The correct solution calculates a tangent of 0.999204" << endl; cout << "Testing with degrees = 112.1..." << endl; cout << " Your solution calculated a tangent of "; tanDegrees(112.1); cout << endl; cout << " The correct solution calculates a tangent of -2.46973"; }

Below is one way to complete the program. You need to make sure to convert your angle to radians before doing any calculations with sinusoidal functions.

#include <iostream> #include <cmath> using namespace std; void tanDegrees (double degrees) { double radians = degrees * (2 * 3.14) / 360.0; double tangent = tan(radians); cout << tangent; }

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Selecting from: functions_a10, functions_a10_pp

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