Mathematics
In the figure (2) given below, ∆ABC is right-angled at B. If AB = y units, BC = 3 units and CA = 5 units, find
(i) sin x°
(ii) y.
Trigonometrical Ratios
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Answer
(i) By formula,
sin x° =
= .
Hence, sin x° = .
(ii) In right-angled ∆ABC
Using pythagoras theorem
⇒ AC2 = BC2 + AB2
⇒ AB2 = AC2 - BC2
⇒ y2 = 52 - 32
⇒ y2 = 25 - 9
⇒ y2 = 16
⇒ y =
⇒ y = 4.
Hence, y = 4 units.
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