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Răspuns:
cos²45° - sin²30° = 1/4
Explicație pas cu pas:
cos²45° - sin²30° = ?
cos 45° = √2/2 => cos²45° = (√2/2)² = 2/4
sin 30° = 1/2 => sin²30° = (1/2)² = 1/4
=> cos²45° - sin²30° = 2/4 - 1/4 =>
cos²45° - sin²30° = 1/4