Evaluate : cos2 25° - sin2 65° - tan2 45°

cos2 25° - sin2 65° - tan2 45° = cos2 (90° - 65°) - sin2 65° - tan2 45° = sin2 65° - sin2 65° - tan2 45° = - tan2 45° = - 1 Hence, cos2 25° - sin2 65° - tan2 45° = -1.

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Mathematics

Evaluate :
cos² 25° - sin² 65° - tan² 45°

Trigonometric Identities

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Answer

cos² 25° - sin² 65° - tan² 45°

= cos² (90° - 65°) - sin² 65° - tan² 45°

= sin² 65° - sin² 65° - tan² 45°

= - tan² 45°

= - 1

Hence, cos² 25° - sin² 65° - tan² 45° = -1.

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Mathematics

Evaluate :
cos² 25° - sin² 65° - tan² 45°

Trigonometric Identities

Answer

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Mathematics

Evaluate :cos2 25° - sin2 65° - tan2 45°

Trigonometric Identities

Answer

Related Questions

Evaluate :sin2 35° - cos2 55°

Evaluate :cot 54°tan 36°\dfrac{\text{cot 54°}}{\text{tan 36°}}tan 36°cot 54°​ + tan 20°cot 70°\dfrac{\text{tan 20°}}{\text{cot 70°}}cot 70°tan 20°​ - 2

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Show that :tan 10° tan 15° tan 75° tan 80° = 1

Evaluate :
cos² 25° - sin² 65° - tan² 45°

Evaluate :
sin² 35° - cos² 55°

Evaluate :
$\dfrac{\text{cot 54°}}{\text{tan 36°}}$ + $\dfrac{\text{tan 20°}}{\text{cot 70°}}$ - 2

Evaluate :
$\Big(\dfrac{\text{sin 77°}}{\text{cos 13°}}\Big)^2$ + $\Big(\dfrac{\text{cos 77°}}{\text{sin 13°}}\Big)^2$ - 2 cos² 45°

Show that :
tan 10° tan 15° tan 75° tan 80° = 1