1. ABCD is a quadrilateral in which angle A = angle C and angle B = angle D Prove that, if the opposite angles of a quadrilateral are equal, then the quadrilateral is a
parallelogram.

Quadrilateral ABCD is a parallelogram, quadrilateral with opposite sides parallel

Step-by-step explanation:

Statement,                                       Reason

∠A = ∠C,                                          Given

∠B = ∠D,                                          Given

Therefore, we have

∠A + ∠B + ∠C + ∠D = 360°,            Sum of interior angles of a quadrilateral

2×∠A + 2×∠B = 360°,                         Substitution property of equality

∴ ∠A + ∠B = 360°/2 = 180°

∠A + ∠B, are supplementary  angles,   Angles that sum up to 180°

Similarly,

∠C + ∠D, are supplementary  angles,   Angles that sum up to 180°

Therefore, segment DA is parallel to segment BC, (Lines with supplementary angles on the same side of the transversal)

Similarly, given ∠A = ∠C and ∠B = ∠D, we have;

∠A + ∠D and ∠C + ∠B are supplementary  angles,   Angles that sum up to 180°

Therefore, segment AB is parallel to segment DC, (Lines with supplementary angles on the same side of the transversal)

Therefore;

Quadrilateral ABCD is a parallelogram, quadrilateral with parallel opposite sides.

something that characterises a right triangle is the fact that we may use pythagoras' theorem to find any one of its sides given that we have the length of the other two sides. here, we have the length of the hypotenuse, √(87) yd, and one other side, √(23) yd, thus we can easily find the length of the remaining side using pythagoras' theorem as defined below:

c^2 = a^2 + b^2, where c is the length of the hypotenuse, and a and b are the lengths of the other two sides.

thus, given that c = √(87) and a = √(23), we may substitute these into the formula we defined above to get:

c^2 = a^2 + b^2

(√87)^2 = (√23)^2 + b^2 (substitute c = √87 and a = √23 into the equation)

87 = 23 + b^2 (evaluate (√87)^2 = 87 and (√23)^2 = 23 - remember that the square root of a number, squared will equal that very same number)

64 = b^2 (subtract 23 from both sides)

√64 = b (take the square root of both sides)

8 = b (evaluate √64 = 8)

therefor, the length of the unknown leg in the right triangle is 8 yd (first answer).

351°f

step-by-step explanation: