CBSE > Class 09 > Mathematics | CBSE Board | Homework Help

Let {tex}\triangle{/tex}ABC be an equilateral triangle.
We know that in an equilateral triangle the altitude is same as the median.
So, BD=DC=a cm
By Pythagoras theorem,
AC²=AD²+DC²
{tex}\Rightarrow{/tex} AD²=AC²-DC²
{tex}\Rightarrow{/tex} AD²=(2a)² -a²
{tex}\Rightarrow{/tex} AD²= 4a² - a²
{tex}\Rightarrow{/tex} AD²=3a²
{tex}\Rightarrow{/tex} AD={tex}\sqrt 3 {/tex} a cm
So, length of the altitude is {tex}\sqrt 3 {/tex} a cm.

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If the area of an equlateral triangle is 81underroot 3

Posted by Kashish Kashish 5 years, 2 months ago

CBSE > Class 09 > Mathematics

1 answers

Firoj Khan 5 years, 2 months ago

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How to prove the angle sum property of a triangle??

Posted by Samiksha Joshi 5 years, 2 months ago

CBSE > Class 09 > Mathematics

2 answers

Mr Mady 5 years, 2 months ago

Take a line parallel to the base . Angle 1 on top angle 2 on either right or left and third one on the third space.The sides (other than base) form transversal on two parallel lines. 1+4+5=180° on the line parallel to base 2=4 and 3=5 both alternate interior angles .So 1+4+5=180° then 1+2+3=180°(proved)

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Firoj Khan 5 years, 2 months ago

A+b+c=180

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Find a rational number between -2 and 4

Posted by Mohd Asif 5 years, 2 months ago

CBSE > Class 09 > Mathematics

5 answers

Ramavath Karanusha 5 years, 2 months ago

-1, 0,1,2,3

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Ankit Kumar 5 years, 2 months ago

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Firoj Khan 5 years, 2 months ago

2 3 4

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Shashank Gupta 5 years, 2 months ago

2 3 4

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Shreya Raj 5 years, 2 months ago

2,3

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ANSWER

Find a rational number between 1/9 and 2/9

Posted by Mohd Asif 5 years, 2 months ago

CBSE > Class 09 > Mathematics

2 answers

Gaurav Seth 5 years, 2 months ago

Let us take 4 rational number between 1/9 and 2/9
So, 4+1=5

1/9 and 2/9
1/9x5/5=5/45
2/9x5/5=10/45

Hence, The rational number between 1/9 and 2/9 are
6/45,7/45,8/45,9/45

Rational number between

Are

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Mohd Asif 5 years, 2 months ago

Find a rational number between 1/9 and 2/9

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X=9-4√5 X^-1/x^

Posted by Jitesh Prajapati 5 years, 2 months ago

CBSE > Class 09 > Mathematics

0 answers

ANSWER

Simplify 81x¹² - 256y¹²

Posted by Naveendeep G N 5 years, 2 months ago

CBSE > Class 09 > Mathematics

1 answers

Shreya Raj 5 years, 2 months ago

(9x^6 )^2 -(16y^6)^2 (9x^6+16y^6)(9x^6-16y^6) (9x^6+16y^6)[(3x^3)^2-(4y^3)^2] (9x^6+16y^6)(3x^3+4y^3)(3x^3-4y^3)

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103³

Posted by Shameema Salam11 5 years, 2 months ago

CBSE > Class 09 > Mathematics

2 answers

Mr Mady 5 years, 2 months ago

(100+3)^3 = 100^3+3^3+3(100^2)(3)+3(100)(3^2) = 1000000+27+90000+27001 = 1092727

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No One 5 years, 2 months ago

103×103×103

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What is (a+b)²

Posted by Anshit Tardeja 5 years, 2 months ago

CBSE > Class 09 > Mathematics

2 answers

Naveendeep G N 5 years, 2 months ago

a² + b²+2ab

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Manoj Das 5 years, 2 months ago

a2+b2+2ab

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Show that sum of all sides of a quadrilateral is greatet than the sum of its diagonals

Posted by Sree Kala 5 years, 2 months ago

CBSE > Class 09 > Mathematics

1 answers

Sia ? 5 years, 2 months ago

Given: A quadrilateral ABCD
To prove: The sum of all the sides is greater than the sum of its diagonals.
i.e. AB + BC + CD + DA > AC + BD
Construction: Join AC and BD.
Proof: Since sum of any two sides of a triangle is greater than the third side.
Therefore,
In {tex}\triangle{/tex}ABC
AB + BC > AC ...(i)
In {tex}\triangle{/tex}ACD
AD + DC > AC ...(ii)
In {tex}\triangle{/tex}ABD
AB + AD > BD ...(iii)
and in {tex}\triangle{/tex}BCD
BC + CD > BD ...(iv)
adding (i), (ii), (iii) and (iv) we get
2AD + 2DC + 2AB + 2BC > 2AC + 2BD
{tex}\Rightarrow{/tex} AB + BC + CD + DA > AC + BD
Hence proved.