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Definition of Cosine Calculator

Online cosine definition calculator. Enter the adjacent side and hypotenuse of a right triangle to find cos A=adjacent/hypotenuse—ideal for trigonometry basics.

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cos A = adjacent / hypotenuse
邻边斜边A
Leg next to A
Longest side

📖 Tutorial | Cosine

1. Definition
In a right triangle, cosine of A is adjacent over hypotenuse.
2. Formula & Notation
AdjacentLeg next to A
HypotenuseLongest side
cos Aadj/hyp
3. Properties & Laws
  • cos A = adjacent/hypotenuse;
  • 0
  • cos30°=√3/2, 45°=√2/2, 60°=1/2;
  • Larger angle, smaller cosine.
4. Steps
  1. Enter adjacent and hypotenuse;
  2. Click "Find cos A";
  3. Or click "Load Example".
5. Worked Examples
Example: adjacent 4, hypotenuse 5.
Solution: cos A = 0.8.
6. Common Pitfalls
Adjacent, not opposite;
Hypotenuse longest;
Cosine decreases as angle grows.

❓ FAQ | Cosine

Definition?
Adjacent over hypotenuse.
Adj4 hyp5?
0.8.
Range?
0 to 1.
Special angles?
30°√3/2, 45°√2/2, 60°1/2.
With sine?
sin²A+cos²A=1.
Angle vs cosine?
Larger angle, smaller cosine.