Question

try these on page no (123) class 7
please anyone give me step by step explanation for writting in copies it's important​

Answer 1

Answer:

Before getting onto the question, let's keep in mind that:

• In an isosceles triangle, base angles opposite to the equal sides are equal!
• The sum of all angles in a triangle is 180°!

i) Value of x = 40°

Reason: The value of x will be the same as the other base angle opposite to the equal sides marked.

ii) Value of x = 90°

Reason: The value of x will be be the sum of the base angles subtracted from 180°. Given, the measure of one of the base angles is 45°, so according to the rule, the other base angle's measure will be the same. Hence, value of x = 180° - ( 45° + 45°) = 90°

iii) Value of x = 50°

Reason: The value of x will be the same as the other base angle opposite to the equal sides marked.

iv) Value of x = 40°

Reason: Here, x is one of the base angles opposite to the equal sides, so the other base angle will be the same as x. Using the angle sum property of the triangle, we know that 100° + (x + x) = 180° or 100° + 2x = 180°. So we solve the equation :-

• 2x = 180° - 100° (transposing 100° to the RHS)
• 2x = 100°
• x = 100°/2 (transposing 2 to the the RHS)
• x = 50°

v) Value of x = 45°

Reason: Again, x is one of the base angles opposite to the equal sides, so the other base angle will be the same as x. Using the angle sum property of the triangle, we know that right angle (90°) + (x + x) = 180° or 90° + 2x = 180°. So we solve the equation:-

• 2x = 180° - 90° (transposing 90 to the RHS)
• 2x = 90°
• x = 90°/2 (transposing 2 to the RHS)
• x = 45°

vi) Value of x = 70°

Reason: Again, x is one of the base angles opposite to the equal sides, so the other base angle will be the same as x. Using the angle sum property of the triangle, we know that 40° + (x + x) = 180° or 40° + 2x = 180°. So we solve the equation:-

• 2x = 180° - 40° (transposing 40° to the RHS)
• 2x = 140°
• x = 140°/2 (transposing 2 to the RHS)
• x = 70°

All the best! :D