sin10°sin50°sin70°=1/8. prove it
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Step-by-step explanation:
sin10°sin50°sin70°=1/8. prove it
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Step-by-step explanation:
sin10. sin50. sin 70
sin10. sin(60-10).sin(60+10)
1/2(2sin10.sin50.sin70)
we know that 2sinA.sinB=cos(A-B).COS(A+B)
Then1/2(2sin10.sin50, sin70) =1/2(sin10(cos 20-cos120)
And cos 20=cos(90+30)=1/2
so1/2(sin10(cos20+1/2)
1/2sin10.cos20+1/4sin10
1/4(sin30-sin10)+1/4sin10
1/4sin30
1/4*1/2
1/8(proved)
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