Found this incredible function on my Fx991EX if you press shift and Option button on left corner it creates a QR code that can be scanned with a phone to see graphing
fx991EX Functions, Tables, Regressions and Visualization with QR Code Mini-Math Lesson) - YouTube
Fx 991ex Plus New Scientific Function Calculator Used - Temu Oman
Casio FX-991EX Original Scientific Calculator Classwiz 552 function Sp — Finest Time
Trigonometric functions using Casio 991EX calculator - YouTube
Multifunctional function calculator, special scientific calculator for students' examination,FX-991EX Classwiz Non-Programmable Scientific Calculator, 240 Functions - Walmart.com
CASIO FX-991EX Classwiz Advanced Scientific Calculator - 552 Functions – In Deals We Trust