Answer:
0.308973
-sin 15°
Explanation:
cos 2π/5 = cos 2 * π/5 = cos² π/5 - sin² π/5 = (0.8090)² - (0.5878)² = 0.308973
sin 10° cos 25° - cos 10° sin25° = sin (10° - 25°) = sin -15° = - sin 15°
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