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In the given figure, AD is perpendicular to BC. Find: 3 sin x + 4 cos y − 4 tan y - Mathematics

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Question

In the given figure, AD is perpendicular to BC. Find: 
`(3)/("sin"  x) + (4)/("cos"  y) - 4 "tan"  y`

Sum

Solution


ΔADB is a right-angled triangle.
∴ AB2
= AB2 + BD2
= 122 + 162
= 144 + 256
= 400
⇒ AB = 20cm
ΔADC is a right-angled triangle.
∴ AC2
= AD2 + DC2
= 122 + 92
= 144 + 81
= 225
⇒ AC = 15cm

`(3)/("sin"  x) + (4)/("cos"  y) - 4 "tan"  y`

= `(3)/("AD"/"AB") + (4)/("AD"/"AC") - 4 xx "CD"/"AD"`

= `(3)/(12/20) + (4)/(12/15) - 4 xx (9)/(12)`

= `(60)/(12) + (60)/(12) - 3`
= 5 + 5 - 3
= 7.

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Reciprocal Relations
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Chapter 26: Trigonometrical Ratios - Exercise 26.1

APPEARS IN

Frank Mathematics [English] Class 9 ICSE
Chapter 26 Trigonometrical Ratios
Exercise 26.1 | Q 20.4
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