Page 28 - 機械群機械力學升學寶典

ዚ૛ɢኪ

觀念活絡通數學

2
1. νྡ 2-4 הͪdsinθ = icosθ = itanθ = dόʕ r =

2. sin30° = isin45° = isin60° =
r
y
3. cos30° = sin = icos45° = sin = i θ
x
cos60° = sin = 圖 2-4

2
2
4. ߰ tanφ = 1 dۆ φ = ccc 5. sin θ + cos θ =
2
6. tan30° = itan45° = itan60° =

ഈ 1. y i x i y ix + y c2. 1 i 2 i 3 c3. 60°i 3 i45°i 2 i30°i 1 c
2
2
r r x 2 2 2 2 2 2
−1 1 1 3
4. tan c5. 1c6. €א i1i 3
2 3 3

精選範例 1 同步練習 1

νɨྡהͪd༊ਗ਼ 50N ٙ F ɢʱ༆މɓ νɨྡהͪd༊Ӌ 200N ٙ F ɢί xey

˥̻ʱɢʿɓٜۧʱɢf ˙Σٙʱɢf

y y
F=50N
F=200N

60° 30° x
x

༆ ΋ਗ਼ʱɢٙɽʃʿ˙Σ೥̈dνɨྡ ഈ

F=50N y

F y
60°
x
F x
F x = –50 × cos60° = –25€Nd 

F y = 50 × sin60° = 25 3 €Nd 

18

BD111_CH02.indd 18 23/7/2021 14:56:46