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In the given figure, AD is perpendicular to BC. Find: 5 cos x - Mathematics

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Sum

In the given figure, AD is perpendicular to BC. Find: 5 cos x

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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
5 cos x 

= `5 xx "BD"/"AB"`

= `5 xx (16)/(20)`
= 4.

Concept: Reciprocal Relations
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APPEARS IN

Frank Class 9 Maths ICSE
Chapter 26 Trigonometrical Ratios
Exercise 26.1 | Q 20.1
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