Electronics MK51
You can add, subtract, multiply, divide, calculate natural and common logarithms, direct and inverse trigonometric functions, the return value, factorial, calculations with two-level brackets, squaring and square root, exponentiation, and extracting roots, memory operations, statistical calculations, correction of erroneously entered numbers, operations, and values for the statistical calculations, convert expressed in degrees, minutes and seconds, integers and decimal degrees. In short, an engineering marvel '90s, and even 80s.
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