YC
XB
YC
XB
B
Fig. 1.71
2. In A ABC, B - D-C and BD = 7,
BC = 20 then find following ratios.
(1) A(A ABD)
A(A ADC)
A(A ABD)
(2)
A(A ABC)
(3)
A(A ADC)
A(A ABC)
B
D
Fig. 1.72
3. Ratio of areas of two triangles with equal heights is 2 : 3. If base of the smaller
triangle is 6 cm then what is the corresponding base of the bigger triangle ?
D
4.
In fiquo 1 7
Ana
Answers
Answer:
Similarity Let’s study. • Ratio of areas of two triangles • Basic proportionality theorem • Converse of basic proportionality theorem • Tests of similarity of triangles • Property of an angle bisector of a triangle • Property of areas of similar triangles • The ratio of the intercepts made on the transversals by three parallel lines Let’s recall. We have studied Ratio and Proportion. The statement, ‘the numbers a and b are in the ratio m ’ is also written as, ‘the numbers a and b are in proportion m:n.’ For this conncept we consider positive real numbers. We know that the lengths of line segments and area of any figure are positive real numbers. We know the formula of area of a triangle. Area of a triangle = 1 Base ´ Height 2 Let’s learn. Ratio of areas of two triangles Let’s find the ratio of areas of any two triangles. Ex. In D ABC, AD is the height and BC P is the base. A CQS R Fig. 1.2 In D PQR, PS is the height and D Fig. 1.1 QR is the base 1 2 A( D ABC) = ´ BC ´ AD B A( D PQR) 1 ´ QR ´ PS 2 1