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The value of tan20 ° + tan40 ° + 3tan20 ° · tan40 ° is () A. 3B. -3C. 33D. -33
Tan20 ° + tan40 ° + 3tan20 ° · tan40 ° = Tan (20 ° + 40 °) [1-tan20 ° tan40 °] + 3tan20 ° tan40 ° = 3 [1-tan20 ° tan40 °] + 3tan20 ° tan40 ° = 3-3tan20 ° tan40 ° + 3tan20 ° tan40 ° = 3, so select a
How can tan15 ° = (1-cos30 °) / sin20 ° be deduced
It is Tan 15 ° = (1 - cos 30 °) / sin 30 ° = = = = Tan 15 ° = sin 15 ° / cos 15 ° = 2 (sin 15 °) ^ 2 / (2 sin 15 ° cos 15 °) = (1 - cos 30 °) / sin 30 °. = = = = = in addition, Tan 15 ° = sin 15 ° / cos 15 ° = (2
Comparison size: sin20 ° greater than or less than sin50 °
sin20°=0.34202014332566873304409961468226
sin50°=0.76604444311897803520239265055542
So sin20 ° is less than sin50 °
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