math 請教

2010-08-08 2:24 am
不用計算機,,計以下各式:
tan^2 30°‧sin^2 45°/cos^2 60°

sin^2 45°-cos^2 45+sin30°‧cos60°+tan60°

回答 (4)

2010-08-08 2:42 am
✔ 最佳答案
首先你要知道一些特殊角的三角函數值:
sin 0°=0,sin 30°=1/2,sin 45°=(√2)/2,sin 60°=(√3)/2,sin 90°=1
cos 0°=1,cos 30°=(√3)/2,cos 45°=(√2)/2,cos 60°=1/2,cos 90°=0
tan 0°=0,tan 30°=(√3)/3,tan 45°=1,tan 60°=√3,tan 90°不存在
以上這些是要背的,
然後就可以根據上表內容計算了:
1. tan^2 30°‧sin^2 45°/cos^2 60°
=[(√3)/3]^2 ‧ [(√2)/2]^2 / (1/2)^2
=(3/9)‧(2/4) / (1/4)
=(1/6)‧4
=2/3

2. sin^2 45°-cos^2 45+sin30°‧cos60°+tan60°
=[(√2)/2]^2 - [(√2)/2]^2 + (1/2)‧(1/2) + √3
=1/4+ √3
~~希望可以幫到你~~
2010-08-08 5:18 am
三角函數值(30,60,90度)
是有方法去記.
2010-08-08 2:49 am
tan^2 30°‧sin^2 45°/cos^2 60°
(sqrt3)^2*((sqrt2)/2)/(1/2)^2

(1/sqrt3)^2*((sqrt2)/2)/(1/2)^2
1/3x2
=2/3
_________________________________-
sin^2 45°-cos^2 45+sin30°‧cos60°+tan60°
(sqrt2/2)^2-(sqrt2/2)^2+(1/2)*(1/2)+sqrt3
(1/4)+sqrt3
2010-08-08 2:32 am
不用計算機,,計以下各式:
Tan^2 30°‧Sin^2 45°/Cos^260°
=(1/3)*(1/2)/(1/4)
=4/6
=2/3

Sin^2 45°-Cos^2 45+Sin30°‧Cos60°+Tan60°
=(1/2)-(1/2)+(1/2)*(1/2)+√3
=1/4+√3




收錄日期: 2021-04-13 17:25:30
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