Deli ED991ES Scientific Calculator has 417 Functions. Easy to understand and display as on textbook. 8 Calculating modes. Dual power Solar and Battery. 1 Million lifetime press button. Sliding protective cover. 2-Line display. Functions: Scientific constant. Solve function. Formula and formula set. Sum (Σ)t. Differential, Integration, Equation, Matrix, Vector calculation. (CMPLX). Metric conversions. Calculates in BIN, OCT, DEG, and HEX. Converts BIN, OCT, DEG, HEX. Variables. Statistics calculations. Regression calculation. Fractional arithmetic function, Standard deviation calculation. ANS function. Generate random numbers. Auto power off. Logarithmic functions, using base 10 or base e. Factorial, permutation and combination calculation. Degree, radian, and grad conversion. Trigonometric functions/inverse trigonometric functions.