Sin A, cos A and tan A
Sin A, cos A, and tan A are the basic trigonometric ratios formed from the opposite, adjacent, and hypotenuse sides of a right triangle.
Practice This ConceptMain explanation
Teacher explanation
These three ratios are the starting point of the chapter. Sine uses opposite over hypotenuse, cosine uses adjacent over hypotenuse, and tangent uses opposite over adjacent. If the sides are identified correctly, the ratio becomes simple and direct.
Example
If for angle A the opposite side is 4 cm, adjacent side is 3 cm, and hypotenuse is 5 cm, then sin A = 4/5, cos A = 3/5, and tan A = 4/3.
Simple analogy
Sine and cosine keep the hypotenuse in the denominator; tangent stays in the triangle.
Common confusion
Students often write tan A as adjacent divided by opposite, but that is actually cot A.
Exam tip
Remember the order with a short check: sine and cosine both use the hypotenuse, while tangent does not.
Answer writing and exam use
1-mark use
Write the exact meaning of sin a, cos a and tan a in one clean line.
2-mark use
Define sin a, cos a and tan a and add one example or condition.
3-mark use
Explain sin a, cos a and tan a, show the method or example, and mention the common mistake.
Practice this concept with focused MCQs
Open the concept quiz intro first, review the test details, and then start a focused MCQ set from this concept only. Instant score and answer review are live now.
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