Constructions of Triangles — MATHEMATICS STD 9 — Question
ICSE BoardEnglish MediumSTD 9MATHEMATICSConstructions of Triangles5 Marks
Question
Construct an isosceles triangle using the given data: Altitude $RM = 5\ cm$ and vertex $\angle R = 120^\circ $
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Answer
Altitude $RM = 5\ cm$ and vertex $\angle R = 120^\circ $
Steps of construction:
$1.$ Draw a line $SU$ of any length.
$2.$ Take a point $M$ on $SU.$
$3.$ Through the point $M$ on $SU$ draw $NM$ perpendicular to $SU.$
$4.$ With $M$ as centre and radius $5 \ cm$, draw an arc to cut $N M$ at $R$.
$5.$ Construct $\angle MRP =\angle MRQ =\frac{1}{2} \times 120^{\circ}=60^{\circ}$.
$(a)$ With $R$ as centre, draw an arc cutting $RM$ at $L$.
$(b)$ With $L$ as centre and same radius, cut the arc at $X$ and $Y$.
$(c)$ Join $RX$ and $44$ and produce them to $T$ and $V$ respectively. $R T$ and $R V$ make an angle of $60^{\circ}$ with $Rm.$
$(d)$ Mark the points as $P$ and $Q$ where $RT$ and $RV$ meet $SU.$
Thus, $\text{PQR}$ is the required triangle.
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