Question
From the given figure, in $\triangle A B C$, if $A D \perp B C, \angle C=45^{\circ}, A C=8 \sqrt{2}, B D=5$, then for finding value of $A D$ and $BC$, complete the following activity.

Activity: In $\triangle ADC$, if $\angle ADC =90^{\circ}, \angle C =45^{\circ}$ [Given]
$\therefore \angle DAC =\square \quad$..... [Remaining angle of $\triangle ADC ]$
By theorem of $45^{\circ}-45^{\circ}-90^{\circ}$ triangle,
$ \therefore \square=\frac{1}{\sqrt{2}} AC \text { and } \square=\frac{1}{\sqrt{2}} AC$
$\therefore AD =\frac{1}{\sqrt{2}} \times \square \text { and } DC =\frac{1}{\sqrt{2}} \times 8 \sqrt{2}$
$\therefore AD =8 \text { and } DC =8$
$\therefore BC = BD + DC$
$=5+8$
$=13 $

Answer

In $\triangle MNK , \angle MNK =90^{\circ}, \angle M =45^{\circ}$ [Given]
$\therefore \angle K=45^{\circ}$
..... [Remaining angle of $\triangle M N K$ ]
By theorem of $45^{\circ}-45^{\circ}-90^{\circ}$ triangle,
$\therefore MN =\frac{1}{\sqrt{2}} MK$ and $KN =\frac{1}{\sqrt{2}} MK$
$\therefore MN =\frac{1}{\sqrt{2}} \times 6$ and $KN =\frac{1}{\sqrt{2}} \times 6$
$\therefore MN =\frac{1 \times 6 \times \sqrt{2}}{\sqrt{2} \times \sqrt{2}}$ and $KN =\frac{1 \times 6 \times \sqrt{2}}{\sqrt{2} \times \sqrt{2}}$
... [Multiply numerator and denominator by $\sqrt{2}$ ]
$\therefore MN =\frac{6 \times \sqrt{2}}{2}$ and $KN =\frac{6 \times \sqrt{2}}{2}$
$\therefore MN =3 \sqrt{2}$ and $KN =3 \sqrt{2}$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Similar questions

A ladder $10\ m$ long reaches a window $8\ m$ above the ground. Find the distance of the foot of the ladder from the base of wall. Complete the given activity.
Activity: As shown in figure suppose

PR is the length of ladder $=10 m$
At P - window, At Q - base of wall, At R - foot of ladder
$\therefore PQ =8 m$
$\therefore Q R=?$
In $\triangle P Q R, m \angle P Q R=90^{\circ}$
By Pythagoras Theorem,
$\therefore PQ ^2+\square= PR ^2$
Here, $P R=10, P Q=\square$
From equation (l)
$ 8^2+Q^2=10^2$
$Q R^2=10^2-8^2$
$Q R^2=100-64$
$Q R^2=\square$
$Q R=6 $
$\therefore$ The distance of foot of the ladder from the base of wall is $6 m$.
Complete the following activity, to find the two-digit numbers which are divisible by 6.

Image
Write the correct number in the given boxes from the following A. P.
– 3, – 8, – 13, – 18, . . .
$\text { Here } t _3=\square, t _2=\square, t _4=\square, t _1=\square $
$ t _2- t _1=\square, t _3- t _2=\square $
$ \therefore a =\square, d =\square$
To check the rule for the terms of the sequence look at the arrangements and fill the empty boxes suitably.
1,4,7,10,13,…
Image
Write the correct number in the given boxes from the following $A. P.$
$70, 60, 50, 40, . . .$
Here $t _1=\square, t _2=\square, t _3=\square, \ldots$
$\therefore  a =\square, d =\square$
In ∆ABC,∠ACB is obtuse angle, seg AD ⊥ seg BC. Prove that:
AB² = BC² + AC² - 2BC×CD
The first term and the common difference of an A.P. are 6 and 3 respectively. Find $S_{27}$.

Image
First term and common difference of an A.P. are 6 and 3 respectively ; find $S_{27}$.
$a=6, d=3, s_{27}=?$
$ S _{ n }  =\frac{ n }{2}[\square+( n -1) d ] $
$ S _{27}  =\frac{27}{2}[12+(27-1) \square] $
$ =\frac{27}{2} \times \square $
$ =27 \times 45=\square$