sin20*(4 plus sec20*)
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sin(20°){4 + sec(20°)} = sin(20°) { 1 + [4 cos(20°)} /cos(20°)] = [sin(20°) + 4 sin(20°) cos(20°)] / cos(20°)
= [sin(20°) + 2sin(40°)]/cos(20°)
expressing sin(40°) = sin(60° - 20°)
= [sin(20°) + (√3)cos(20°) - sin(20°)]/cos(20°)
= (√3)cos(20°)/cos(20°) = √3
= [sin(20°) + 2sin(40°)]/cos(20°)
expressing sin(40°) = sin(60° - 20°)
= [sin(20°) + (√3)cos(20°) - sin(20°)]/cos(20°)
= (√3)cos(20°)/cos(20°) = √3
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