Confused on what should be negative when finding with half angle

ECG Axis Interpretation • LITFL • ECG Library Basics

When half angle formulas are positive or negative

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Half-angle identitiespositive or negative?

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Is it possible that the value of sin is negative in a half angle formula? - Quora

Half Angle Identities to Evaluate Trigonometric Expressions

Half Angle Formula Positive or Negative?

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