Mathematics · University
Determinant of a 3 × 3 triangular matrix · formula reference
Off-diagonal entries do not enter this special-case determinant; this is not true for every matrix.
Formula
Off-diagonal entries do not enter this special-case determinant; this is not true for every matrix.
det A = product of diagonal entries (triangular A)
Worked example
Find det A for A = [[-2,6,6],[0,4,12],[0,0,5]]. Round the final result to 4 decimal places if needed.
A is upper triangular, so det A = (-2)(4)(5).
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Prerequisites and checking
Algebra; calculus or linear algebra as appropriate to the topic. Keep units and rounding consistent. State the model conditions before applying the formula.
Further reading and review references
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