Which mathematical product design innovation of the 1970s revolutionized graphing capabilities for students and is credited with significantly changing how mathematics is taught in classrooms?

The design of mathematical tools and products has evolved significantly over time, influenced by both technological advances and changing educational approaches. Today's mathematics products often incorporate elements of gamification, digital interactivity, and visual learning - a stark contrast to tools from previous decades. This poll tests your knowledge about a pivotal product design shift in the mathematics education industry that changed how students interact with mathematical concepts.

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The graphing calculator (with Texas Instruments' TI-83/84 series becoming the industry standard)
The digital protractor with built-in angle measurement display
The Möbius Learning Platform that introduced adaptive mathematical problems
The mechanical formula calculator with interchangeable equation plates