def
definition
def or abbrev
log10Interval
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358def log10Interval : Interval where
359 lo := 230 / 100
proof body
Definition body.
360 hi := 231 / 100
361 valid := by norm_num
362
363/-- log(10) is contained in log10Interval.
364 Proof using log(10) = log(2) + log(5) and Mathlib bounds.
365 log(2) ≈ 0.693, log(5) = log(10/2) requires log(10).
366 Instead: log(10) = 2*log(√10), but √10 computation is circular.
367 Best approach: log(10) = log(2) + log(5) where log(5) = log(4*5/4) = 2*log(2) + log(1.25)
368 So log(10) = 3*log(2) + log(1.25) -/