Ex 8.1, 4 - Chapter 8 Class 10 Introduction to Trignometry

Last updated at April 16, 2024 by Teachoo

Transcript

Ex 8.1, 4
Given 15 cot A = 8, find sin A and sec A.
Given
15 cot A = 8
cot A = ๐/๐๐
Now,
tan A = 1/cotโก๐ด
= 1/(8/15)
= ๐๐/๐
Now,
tan A = 15/8
(๐ ๐๐๐ ๐๐๐๐๐ ๐๐ก๐ ๐ก๐ โ ๐ด)/(๐ ๐๐๐ ๐๐๐๐๐๐๐๐ก ๐ก๐โ ๐ด) = 15/8
๐ฉ๐ช/๐จ๐ฉ=๐๐/๐
Let
BC = 15x
& AB = 8x
Finding AC
Using Pythagoras theorem,
(Hypotenuse)2 = (Height)2 + (Base)2
AC2 = AB2 + BC2
AC2 = (8x)2 + (15x)2
AC2 = 64 x2 + 225 x2
AC2 = 289 x2
AC2 = (17x)2
AC = 17x
Now, we need to find sin A & sec A
sin A = (๐ ๐๐๐ ๐๐๐๐๐ ๐๐ก๐ ๐ก๐ โ ๐ด)/๐ป๐ฆ๐๐๐ก๐๐๐ข๐ ๐
= ๐ต๐ถ/๐ด๐ถ
= 15๐ฅ/17๐ฅ
= ๐๐/๐๐
For sec A , Finding cos A first
cos A = (๐ ๐๐๐ ๐๐๐๐๐๐๐๐ก ๐ก๐ โ ๐ด)/๐ป๐ฆ๐๐๐ก๐๐๐ข๐ ๐
= ๐ด๐ต/๐ด๐ถ
= 8๐ฅ/17๐ฅ
= ๐/๐๐
And,
sec A = 1/cosโกใ ๐ดใ
= 1/(8/17)
= ๐๐/๐

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.

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