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Mathematics 18 Online
NonportritV2:

Seth is using the figure shown below to prove Pythagorean Theorem using triangle similarity. In the given triangle ABC, angle A is 90° and segment AD is perpendicular to segment BC. The figure shows triangle ABC with right angle at A and segment AD. Point D is on side BC. Part A: Identify a pair of similar triangles. (2 points) Part B: Explain how you know the triangles from Part A are similar. (4 points) Part C: If DB = 9 and DC = 4, find the length of segment DA. Show your work. (4 points)

jhonyy9:

please correct it ia think there no segment AD perpendicular to segment BC this AD wan being AB yes ?

NonportritV2:

There is a segment AD.

jhonyy9:

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jhonyy9:

where ?

NonportritV2:

1 attachment
jhonyy9:

and segment AD is perpendicular to segment BC. how is possibly this ?

NonportritV2:

They both have two lines that meet at the same angle

jhonyy9:

may be AD perpendicular on DC and not on BC

jhonyy9:

check this please

NonportritV2:

1 attachment
NonportritV2:

sorry wrong image

jhonyy9:

so than what will be correct ?

jhonyy9:

the second posted image ?

NonportritV2:

the second image is the image for this question the first one was for another question

jhonyy9:

ok so Part A: Identify a pair of similar triangles. (2 points) Part B: Explain how you know the triangles from Part A are similar. (4 points) Part C: If DB = 9 and DC = 4, find the length of segment DA. Show your work. (4 points)

jhonyy9:

step by step please - i m here to help you and explain

jhonyy9:

A . triangle ADB similar triangle ADC ?

NonportritV2:

i would say so they look perpendicular

jhonyy9:

do you wan saying angle D_1 congruent angle D_2 bc. AD perpendicular BC ?

jhonyy9:

and again what can you see there ? side AD what is for these triangles ?

jhonyy9:

AD not is common side ?

NonportritV2:

Answer: Part A; Triangle ABD is similar to Triangle ACD Step-by-step explanation: Part B; The triangle is given such that angle A is 90° If point D is on line BC, then it touches angle A. However line AD is perpendicular to line BC,which means it splits the angle at A into two equal halves. Hence, you now have two right angled triangles, on the one hand, triangle ABD and on the other hand, triangle ACD. The first one has angle D measuring 90° and line AB as the hypotenuse. The second one also has angle D measuring 90° with it's hypotenuse at line AC. Part C; From the dimensions given in the question, triangle ABD has side BD measuring 9 while the other two sides are not given. But angle D is given as 90° (perpendicular line from angle A in the original triangle). Also, angle A has been split in two which makes angle A in triangle ABD to measure 45° Therefore triangle ABD is a right angled triangle with the other two sides measuring 45° each. [180° = (90°+45°+45°)] We can solve for the unknown side by applying trigonometrical ratios. We have line DB given as 9 units and the angle facing it (angle A) is 45°. Line AD is unknown and is also facing angle B which is 45° We shall apply the ratio of tangent of angle since we have the opposite to angle B (unknown) and the adjacent to angle B (9 units) Tan 45° = opposite/adjacent Tan 45° = DA/9 Multiply both sides by 9 9 × Tan 45° = DA (Looking up the table of values for trigonometrical ratios, Tan 45°=1) 9 × 1 = DA Therefore line DA equals 9 units

NonportritV2:

got it ^

jhonyy9:

understandably ?

NonportritV2:

yes sir

jhonyy9:

ok was my pleasure have a nice day

NonportritV2:

thank you.

jhonyy9:

np anytime

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