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How to find complex roots on a TI-89 Titanium

By E-Code · updated

Press F2, then ALPHA = for A:Complex and 1 for cSolve(, type the equation, a comma and the variable and ENTER: cSolve(x^2+1=0,x) gives x = ί or x = -ί, where solve( only says false.

Step by step

  1. Try solve( first. F2 1 X ^ 2 + 1 = 0 , X ) Press F2 1 for solve(, then type x^2+1=0,x and ).
  2. No real answers. ENTER Press ENTER. false means no real number works: x² is never -1.
  3. Open Complex. F2 ALPHA = Press F2, then ALPHA and = for A:Complex. Menu items after 9 are letters, and A is the ALPHA letter on the = key.
  4. Pick cSolve(. 1 Press 1 for cSolve(, which also looks for complex answers.
  5. Type the equation. X ^ 2 + 1 = 0 , X ) Type x^2+1=0,x and ).
  6. Solve it. ENTER Press ENTER.
  7. Read both answers. x = ί or x = -ί, where ί is the square root of -1. cSolve( finds complex answers even in real mode.

What the screen shows

x = ί or x = -ί, where ί is the square root of -1. cSolve( finds complex answers even in real mode.

Look for x = ί or x = -ί on the screen.

Try it with the keys lit up

This guide is one of E-Code's Learn lessons. Open it on E-Code's TI-89 calculator and each key lights up in turn as you press it.

Try “Find complex roots” on the TI-89 calculator

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