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Question
1 +cos 20° +cos 30° +cos 50° = ______.
Options
4 cos 10° cos 15° cos 25°
4 cos 10° cos 20° cos 50°
4 sin 10° sin 15° sin 25°
4 sin 10° sin 20° sin 50°
MCQ
Fill in the Blanks
Solution
1 +cos 20° +cos 30° +cos 50° = 4 cos 10° cos 15° cos 25°.
Explanation:
1 + cos 20° + cos 30° + cos 50°
= 2 cos2 10° + 2 cos 40° cos 10°
= 2 cos 10° (cos 10° + cos 40°)
= 4 cos 10° cos 15° cos 25°
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Factorization Formulae - Formulae for Conversion of Product in to Sum Or Difference
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