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From given figure, In ∆ABC, AB ⊥ BC, AB = BC then m∠A = ?
Concept: Application of Pythagoras Theorem in Acute Angle and Obtuse Angle
If a triangle having sides 50 cm, 14 cm and 48 cm, then state whether given triangle is right angled triangle or not
Concept: Converse of Pythagoras Theorem
A rectangle having dimensions 35 m × 12 m, then what is the length of its diagonal?
Concept: Converse of Pythagoras Theorem
From the given figure, in ∆ABC, if AD ⊥ BC, ∠C = 45°, AC = `8sqrt(2)` , BD = 5, then for finding value of AD and BC, complete the following activity.
Activity: In ∆ADC, if ∠ADC = 90°, ∠C = 45° ......[Given]
∴ ∠DAC = `square` .....[Remaining angle of ∆ADC]
By theorem of 45° – 45° – 90° triangle,
∴ `square = 1/sqrt(2)` AC and `square = 1/sqrt(2)` AC
∴ AD =`1/sqrt(2) xx square` and DC = `1/sqrt(2) xx 8sqrt(2)`
∴ AD = 8 and DC = 8
∴ BC = BD +DC
= 5 + 8
= 13
Concept: Property of 30°- 60°- 90° Triangle Theorem
Complete the following activity to find the length of hypotenuse of right angled triangle, if sides of right angle are 9 cm and 12 cm.
Activity: In ∆PQR, m∠PQR = 90°
By Pythagoras Theorem,
PQ2 + `square` = PR2 ......(I)
∴ PR2 = 92 + 122
∴ PR2 = `square` + 144
∴ PR2 = `square`
∴ PR = 15
∴ Length of hypotenuse of triangle PQR is `square` cm.
Concept: Similarity in Right Angled Triangles
In ∆LMN, l = 5, m = 13, n = 12 then complete the activity to show that whether the given triangle is right angled triangle or not.
*(l, m, n are opposite sides of ∠L, ∠M, ∠N respectively)
Activity: In ∆LMN, l = 5, m = 13, n = `square`
∴ l2 = `square`, m2 = 169, n2 = 144.
∴ l2 + n2 = 25 + 144 = `square`
∴ `square` + l2 = m2
∴By Converse of Pythagoras theorem, ∆LMN is right angled triangle.
Concept: Converse of Pythagoras Theorem
A congruent side of an isosceles right angled triangle is 7 cm, Find its perimeter
Concept: Similarity in Right Angled Triangles
As shown in figure, LK = `6sqrt(2)` then

- MK = ?
- ML = ?
- MN = ?
Concept: Property of 30°- 60°- 90° Triangle Theorem
In ΔABC, ∠ABC = 90°, ∠BAC = ∠BCA = 45°. If AC = `9sqrt(2)`, then find the value of AB.

Concept: Property of 45°- 45°- 90° Triangle Theorem

In the above figure `square`ABCD is a rectangle. If AB = 5, AC = 13, then complete the following activity to find BC.
Activity: ΔABC is a `square` triangle.
∴ By Pythagoras theorem
AB2 + BC2 = AC2
∴ 25 + BC2 = `square`
∴ BC2 = `square`
∴ BC = `square`
Concept: Pythagoras Theorem
In ΔABC, AB = 9 cm, BC = 40 cm, AC = 41 cm. State whether ΔABC is a right-angled triangle or not. Write reason.
Concept: Converse of Pythagoras Theorem
If a and b are natural numbers and a > b If (a2 + b2), (a2 – b2) and 2ab are the sides of the triangle, then prove that the triangle is right-angled. Find out two Pythagorean triplets by taking suitable values of a and b.
Concept: Pythagorean Triplet
Construct two concentric circles with centre O with radii 3 cm and 5 cm. Construct a tangent to a smaller circle from any point A on the larger circle. Measure and write the length of the tangent segment. Calculate the length of the tangent segment using Pythagoras' theorem.
Concept: Pythagoras Theorem
In the right-angled triangle ABC, Hypotenuse AC = 10 and side AB = 5, then what is the measure of ∠A?
Concept: Pythagoras Theorem
If tan θ = `12/5`, then 5 sin θ – 12 cos θ = ?
Concept: Pythagoras Theorem
From the information in the figure, complete the following activity to find the length of the hypotenuse AC.

AB = BC = `square`
∴ ∠BAC = `square`
Side opposite angle 45° = `square/square` × Hypotenuse
∴ `5sqrt(2) = 1/square` × AC
∴ AC = `5sqrt(2) xx square = square`
Concept: Pythagoras Theorem
ΔPQR, is a right angled triangle with ∠Q = 90°, QR = b, and A(ΔPQR) = a. If QN ⊥ PR, then prove that QN = `(2ab)/sqrt(b^4 + 4a^2)`
Concept: Similarity in Right Angled Triangles
If m and n are real numbers and m > n, if m2 + n2, m2 – n2 and 2 mn are the sides of the triangle, then prove that the triangle is right-angled. (Use the converse of the Pythagoras theorem). Find out two Pythagorian triplets using convenient values of m and n.
Concept: Pythagorean Triplet
AB, BC and AC are three sides of a right-angled triangle having lengths 6 cm, 8 cm and 10 cm, respectively. To verify the Pythagoras theorem for this triangle, fill in the boxes:
ΔABC is a right-angled triangle and ∠ABC = 90°.
So, by the Pythagoras theorem,
`square` + `square` = `square`
Substituting 6 cm for AB and 8 cm for BC in L.H.S.
`square` + `square` = `square` + `square`
= `square` + `square`
= `square`
Substituting 10 cm for AC in R.H.S.
`square` = `square`
= `square`
Since, L.H.S. = R.H.S.
Hence, the Pythagoras theorem is verified.
Concept: Pythagoras Theorem
In the given figure, triangle PQR is right-angled at Q. S is the mid-point of side QR. Prove that QR2 = 4(PS2 – PQ2).

Concept: Converse of Pythagoras Theorem
