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Prove the following : sin25*cos5-cos80*sin70=sin15*cos5

Prove the following : sin25*cos5-cos80*sin70=sin15*cos5

Grade:12th pass

3 Answers

Deepak Kumar Shringi
askIITians Faculty 4404 Points
5 years ago
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Aditya Gupta
2081 Points
5 years ago
We use 2sin25*cos 5= sin30+sin20
And 2sin70cos80= sin30-sin10
Subtract
2*LHS= sin20+ sin10= 2sin15cos5
So LHS= RHS
Arun
25750 Points
5 years ago
Dear student
 
This question is purely an application of 
2 sinA cos B
 
Now
 
1/2 (sin 30 + sin 20)  - 1/2 (sin 150  - sin 10)
 
1/2 ( sin 20 + sin10)
 
= 1/2 * 2 sin 15 cos 5 = sin 15 cos 5
 
Hope it helps

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