Trigonometrical Ratios
ICSE · Class 9 · Mathematics
Flashcards for Trigonometrical Ratios — ICSE Class 9 Mathematics. Quick Q&A cards covering key concepts, definitions, and formulas.
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See them allWhat does the word 'Trigonometry' mean?
Answer
Trigonometry means 'measurement of triangles'. In this chapter, we deal specifically with the relations between sides and angles of right-angled triangles.
In a right-angled triangle with angle A as the reference angle, identify the perpendicular, base, and hypotenuse.
Answer
For angle A: Perpendicular = side opposite to angle A, Base = side adjacent to angle A, Hypotenuse = side opposite to the right angle (longest side).
Define sine (sin) of an angle in a right triangle.
Answer
Sine of an angle = Perpendicular/Hypotenuse. For angle A, sin A = opposite side/hypotenuse. It is a ratio and has no units.
Define cosine (cos) of an angle in a right triangle.
Answer
Cosine of an angle = Base/Hypotenuse. For angle A, cos A = adjacent side/hypotenuse. It is a ratio and has no units.
Define tangent (tan) of an angle in a right triangle.
Answer
Tangent of an angle = Perpendicular/Base. For angle A, tan A = opposite side/adjacent side. It is a ratio and has no units.
Define cotangent (cot) of an angle in a right triangle.
Answer
Cotangent of an angle = Base/Perpendicular. For angle A, cot A = adjacent side/opposite side. It is the reciprocal of tangent.
Define secant (sec) of an angle in a right triangle.
Answer
Secant of an angle = Hypotenuse/Base. For angle A, sec A = hypotenuse/adjacent side. It is the reciprocal of cosine.
Define cosecant (cosec) of an angle in a right triangle.
Answer
Cosecant of an angle = Hypotenuse/Perpendicular. For angle A, cosec A = hypotenuse/opposite side. It is the reciprocal of sine.
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