Which groundbreaking design feature did Texas Instruments introduce in their 1976 TI-30 calculator that revolutionized mathematics education?

The handheld calculator transformed mathematics education and professional practice, making complex calculations accessible to everyone. But the journey from bulky desktop machines to sleek pocket calculators involved fascinating design decisions, commercial competition, and technological breakthroughs. Test your knowledge about one of the most influential mathematical product designs in history!

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The first algebraic notation system, replacing Reverse Polish Notation (RPN)
Solar power cells, eliminating the need for batteries in classroom settings
Scientific functions at a consumer-affordable price point (under $25)
The first graphing capability in a handheld device