Prove that Cos(20) Cos(40) Cos(80) = 1/8?

7 ⤊

Prove that Cos(20) Cos(40) Cos(80) = 1/8?

2007-11-30 19:39:51 · 4 answers · asked by Scythian1950 7 in Science & Mathematics ➔ Mathematics

4 answers

Cos(20) Cos(40) Cos(80)
= [1/sin(20)](1/2)[2sin(20)Cos(20) Cos(40) Cos(80)]
= [1/sin(20)](1/4)[2sin(40)Cos(40) Cos(80)]
= [1/sin(20)](1/8)[2sin(80)Cos(80)]
= [1/sin(20)](1/8)sin(160)
= 1/8, since sin(160) = sin(20)

2007-11-30 19:48:45 · answer #1 · answered by sahsjing 7 · 6⤊ 0⤋

Cos20 Cos40 Cos80

2016-12-12 16:55:31 · answer #2 · answered by ? 4 · 0⤊ 0⤋

where did that 1/sin20 come from?

2015-07-24 05:19:37 · answer #3 · answered by balasiddharth 1 · 0⤊ 0⤋

1 thing always equal another eventually. Thats how a carrot can be a fish and a space alien

2007-11-30 19:42:33 · answer #4 · answered by Anonymous · 1⤊ 10⤋