Product Type: Scientific Calculator Model: FX-991CW 10 2 digits Display Type: Natural Textbook display Power Supply: Solar Battery Natural Textbook display – Input and display fractions, powers, logarithms, roots, and other mathematical formulas and symbols just as they appear in textbooks. Both Solar and Battery powered. Solar powered when light is sufficient, battery powered when light is insufficient. 540 Functions. Battery – Solar and Battery • Plastic keys • Comes with slide on hard case Dedicated keys to convert polar coordinates to rectangular coordinates and vice versa. Specifies degrees, radians, grads as the angle unit for value input and calculation result display. Aids in sexagesimal calculations with respect to decimal conversion.