三角形sin tan cos是怎样做? (詳細的做法)

a^2+b^2=c^2(畢氏定理)
a=最短,b=中間,c=最長

例如一個直角三角形 底是75ft the top of the tower is 78度 高是怎麽?
/| 78度
/ |
/__|
75ft

is it?

tan78 = 75 / 高
高 = 75 / tan78

case 1. 有關直角左右的線用tan
2. 兩線都 touch 到的用 cos
3. 一斜線 & 一線和度相對的用sin

tan = sin / cos

2008-05-27 22:22:18 補充：
候選編號 001

的a^2+b^2=c^2(畢氏定理)

a=最短,b=中間,c=最長

是有問題的!

a 可能 = b

For a right-angled triangle:
let A be the adjacent side, that is the side of the triangle next to the angle.
let O be the opposite side, that is the side opposite to the angle in question,\.
let H be the hypotenus (the sloping side).
Then by definition: sin 78 = O/H, cos78 = A/H and tan78 = O/A.
Now A=75ft, angle is 78, you want to find O, that means you should choose tan78 since H is unknown.
Therefore, tan78=O/75, so we get O=75tan78=352.8ft (4 sig.fig.)