Question :-The value of 2sin10°sin25°+2sin10°sin45°+2sin10°sin65° is equal to?
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Answer:
1 / √2
Step-by-step explanation:
2 sin a sin b = cos ( a - b ) - cos ( a + b )
cos 15- cos 35 + cos 35 - cos 55 + cos 55 - cos 75
= cos 15 - cos 75 = cos 15 - sin 15 = 1 / √2
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