991 Plus—Scientific Calculator

991 Plus is a free scientific calculator and graphing calculator for students, engineers, and professionals — built to work completely offline with a clean, distraction-free interface.

Designed around the layout of the ES Plus scientific calculator series, 991 Plus handles everything from basic school math to advanced university-level calculations with precision and speed.

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🔢 991 PLUS SCIENTIFIC CALCULATOR
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• Natural display — expressions shown exactly as in textbooks
• Trigonometric functions: sin, cos, tan and all inverses
• Logarithms (log, ln) and exponential functions
• Powers, roots, fractions, and percentages
• Complex number calculations (rectangular and polar form)
• Combinations, permutations, GCD, LCM, prime factorization
• High-precision results for engineering-level work

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📈 GRAPHING CALCULATOR
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• Plot multiple functions simultaneously
• Cartesian, polar, and parametric graph modes
• Auto-detect roots, intersections, minimums, and maximums
• Trace mode and tangent line visualization
• Pinch-to-zoom for detailed graph analysis
• Derivative graph overlay

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🧮 EQUATION SOLVER
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• Linear, quadratic, and cubic equation solver
• Systems of equations (2 and 3 unknowns)
• Polynomial solver
• CAS: symbolic calculation and algebraic simplification

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📐 CALCULUS
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• Derivative and differentiation calculator
• Definite and indefinite integral calculator
• Limit calculations
• Taylor series expansion

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📊 STATISTICS & DATA
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• Single-variable and two-variable statistics
• Regression models: linear, quadratic, exponential, logarithmic
• Histograms, box plots, and scatter plots
• Probability distributions: normal, binomial, Poisson

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🟦 MATRIX & VECTOR
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• Matrices up to 10×10: inverse, determinant, transpose
• Vector dot and cross product
• Solve linear systems using matrix operations

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🎨 MODERN INTERFACE
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• Dark theme for comfortable night and low-light use
• Full-screen distraction-free layout
• Smooth animations and responsive design for all screen sizes
• Lightweight and fast — no lag, no unnecessary permissions

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⚡ FULLY OFFLINE
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No internet connection required. 991 Plus runs completely offline — results are instant, anytime, anywhere. Perfect for:
• Exam and classroom use
• Engineering and lab work
• Daily calculations on the go

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✅ WHY 991 PLUS?
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✔ Free — no subscription, no hidden fees
✔ Works 100% offline
✔ Natural display matches real ES Plus calculator layout
✔ Covers algebra, calculus, trigonometry, and statistics
✔ Built for high school, university, and professional use
✔ Lightweight and fast with a clean modern interface

Download 991 Plus today — the free scientific calculator and graphing calculator that fits in your pocket.