c/c++ 实现三角函数（不使用库函数） sin/cos/tan/cot
#include <iostream>#include <cstdlib>#include <iomanip>constexpr auto PI = 3.1415926;int menu_select() {int select;std::cout << "-------Welcome to Snow Calculator-------" << std::endl;std::cout << "1. sin x " << std::endl;std::cout << "2. cos x " << std::endl;std::cout << "3. tan x " << std::endl;std::cout << "4. cot x " << std::endl;std::cout << "5. Clean screen" << std::endl;std::cout << "0. to quit" << std::endl;std::cout << "----------------------------------------" << std::endl;std::cin >> select;return select;}double inputtrans(void) {double x;std::cout << "Please input x: " << std::endl;std::cin >> x;while (x >= 360.0){x -= 360.0;}return (x * PI / 180.0);}double factorial(double n) {if (n <= 1) {return n;}else {return n * factorial(n - 1);}}//下面为求绝对值函数double myabs(double num1){return((num1 > 0) ? num1 : -num1);}//下面为求sin(x)的值double snowsin(double num2){int i = 1, negation = 1;//取反double sum;double index = num2;//指数double Factorial = 1;//阶乘double TaylorExpansion = num2;//泰勒展开式求和do{Factorial = Factorial * ((__int64)i + 1) * ((__int64)i + 2);//求阶乘index *= num2 * num2;//求num2的次方negation = -negation;//每次循环取反sum = index / Factorial * negation;TaylorExpansion += sum;i += 2;} while (myabs(sum) > 1e-15);return(TaylorExpansion);}double snowcos(double x) {x = (PI / 2) - x;return snowsin(x);}double snowtan(double x) {return (snowsin(x) / snowcos(x));}double snowcot(double x) {return (1 / snowtan(x));}int main(){double result = 0.0;double x = 0.0;int menu = menu_select();while (menu != 0){switch (menu){case 1:x = inputtrans();result = snowsin(x);std::cout << std::fixed << std::setprecision(5) << "Result = " << result << std::endl;break;case 2:x = inputtrans();result = snowcos(x);std::cout << std::fixed << std::setprecision(5) << "Result = " << result << std::endl;break;case 3:x = inputtrans();result = snowtan(x);std::cout << std::fixed << std::setprecision(5) << "Result = " << result << std::endl;break;case 4:x = inputtrans();result = snowcot(x);std::cout << std::fixed << std::setprecision(5) << "Result = " << result << std::endl;break;case 5:system("cls");break;case 0:break;default:std::cout << "Wrong input, please input again!" << std::endl;break;}if (menu == 0) {break;}menu = menu_select();}std::cout << "Thank you for using!\nPress any key to exit.\n";system("pause");}
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