Triangles

In figure, two line segments AC and BD intersect each other at the point P such that PA = 6 cm, PB = 3 cm, PC = 2.5 cm, PD = 5 cm, ∠APB = 50° and ∠CDP = 30°. Then, ∠PBA is equal to (a) 50° (b) 30° (c) 60° (d) 100°

Solution: (d) 100° Explanation: From triangles APB and CPD, $\angle APB\text{ }=~\angle CPD\text{ }=\text{ }50{}^\circ $ (as they are vertically opposite angles) $AP/PD\text{ }=\text{ }6/5$ … (i)...

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1. In a Δ ABC, AD is the bisector of ∠ A, meeting side BC at D. (vii) if \[\mathbf{AB}\text{ }=\text{ }\mathbf{5}.\mathbf{6}\text{ }\mathbf{cm},\] \[\mathbf{BC}\text{ }=\text{ }\mathbf{6}\text{ }\mathbf{cm},\] and \[\mathbf{BD}\text{ }=\text{ }\mathbf{3}.\mathbf{2}\text{ }\mathbf{cm},\] find AC. (viii) if \[\mathbf{AB}\text{ }=\text{ }\mathbf{10}\text{ }\mathbf{cm},\] \[\mathbf{AC}\text{ }=\text{ }\mathbf{6}\text{ }\mathbf{cm},\] and \[\mathbf{BC}\text{ }=\text{ }\mathbf{12}\text{ }\mathbf{cm},\] find BD and DC.

Solution: Given: Δ ABC and AD bisects ∠A, meeting side BC at D.  \[AB\text{ }=\text{ }5.6\text{ }cm,\] \[BC\text{ }=\text{ }6\text{ }cm,\] and \[BD\text{ }=\text{ }3.2\text{ }cm\]....

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10. A triangle has sides \[\mathbf{5}\text{ }\mathbf{cm},\text{ }\mathbf{12}\text{ }\mathbf{cm}\text{ }\mathbf{and}\text{ }\mathbf{13}\text{ }\mathbf{cm}.\]Find the length to one decimal place, of the perpendicular from the opposite vertex to the side whose length is \[\mathbf{13}\text{ }\mathbf{cm}.\]

Solution: From the fig. \[AB\text{ }=\text{ }5cm,\text{ }BC\text{ }=\text{ }12\text{ }cm\text{ }and\text{ }AC\text{ }=\text{ }13\text{ }cm.\] Then, \[A{{C}^{2}}~=\text{ }A{{B}^{2}}~+\text{...

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8. Two poles of height \[\mathbf{9}\text{ }\mathbf{in}\text{ }\mathbf{and}\text{ }\mathbf{14}\text{ }\mathbf{m}\] stand on a plane ground. If the distance between their feet is \[\mathbf{12}\text{ }\mathbf{m},\]find the distance between their tops.

Solution: Comparing with the figure, it’s given that AC = \[14\text{ }m,\text{ }DC\text{ }=\text{ }12m\text{ }and\text{ }ED\text{ }=\text{ }BC\text{ }=\text{ }9\text{ }m\]  Construction: Draw...

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7. The foot of a ladder is \[\mathbf{6}\text{ }\mathbf{m}\] away from a wall and its top reaches a window \[\mathbf{8}\text{ }\mathbf{m}\] above the ground. If the ladder is shifted in such a way that its foot is \[\mathbf{8}\text{ }\mathbf{m}\] away from the wall, to what height does its tip reach?

Solution:       Let’s assume the length of ladder to be, AD = BE = x m So, in ∆ACD, by Pythagoras theorem We have, \[\begin{array}{*{35}{l}}   ...

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6. In an isosceles triangle ABC, AB = \[\mathbf{AC}\text{ }=\text{ }\mathbf{25}\text{ }\mathbf{cm},\text{ }\mathbf{BC}\text{ }=\text{ }\mathbf{14}\text{ }\mathbf{cm}.\]Calculate the altitude from A on BC.

Solution: Given, ∆ABC, AB = AC = \[25\text{ }cm\text{ }and\text{ }BC\text{ }=\text{ }14.\]                                                                             \[\] In ∆ABD and ∆ACD, we see...

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