Value of sinπ/10 × sin13π/10
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To solve : sinπ/10 × sin13π/10
=Sin18°xsin (π+3π/10)
= -sin18°xsin3π/10
= -sin18°sin54°
= -((√5-1)/4)(√5+1)/4)
= -(5-1)/16
= -4/16
= -1/4
∴sinπ/10 × sin13π/10 =-1/4
=Sin18°xsin (π+3π/10)
= -sin18°xsin3π/10
= -sin18°sin54°
= -((√5-1)/4)(√5+1)/4)
= -(5-1)/16
= -4/16
= -1/4
∴sinπ/10 × sin13π/10 =-1/4
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