exp

exp

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Calculates the natural exponential of a number

 #include <math.h> double exp ( double x  ); float expf ( float x  ); long double expl ( long double x  ); 

The return value of the exp( ) function is e raised to the power of the function's argument, or e^x, where e is Euler's number, 2.718281.... If the result is beyond the range of the function's type, a range error occurs.

The natural exponential function exp( ) is the inverse of the natural logarithm function, log( ).

Example

 /* Amount owed = principal * e**(interest_rate * time) */ int principal = 10000;      // Initial debt is ten thousand dollars. int balance = 0; double rate = 0.055;        // Interest rate is 5.5% annually. double time = 1.5;          // Period is eighteen months. balance = principal * exp( rate * time ); printf("Invest %d dollars at %.1f%% compound interest, and "        "in %.1f years you'll have %d dollars.\n",        principal, rate*100.0, time, balance ); 

This code produces the following output:

 Invest 10000 dollars at 5.5% compound interest, and in 1.5 years you'll have 10859 dollars. 

See Also

The C99 exponential functions exp2( ) and expm1( ); the exponential functions for complex numbers: cexp( ), cexpf( ), and cexpl( ); the general exponential function, pow( )