Students sell 80% of the books at a book sale. They sell 48 books in all. How many books are at the book sale?

Here is their argument. given the obtuse angle x, we make a quadrilateral abcd with ∠dab = x, and ∠abc = 90◦, and ad = bc. say the perpendicular bisector to dc meets the perpendicular bisector to ab at p. then pa = pb and pc = pd. so the triangles pad and pbc have equal sides and are congruent. thus ∠pad = ∠pbc. but pab is isosceles, hence ∠pab = ∠pba. subtracting, gives x = ∠pad−∠pab = ∠pbc −∠pba = 90◦. this is a preposterous conclusion – just where is the mistake in the "proof" and why does the argument break down there?

Me. i need an answer asap. , you! select the correct answer from each drop-down menu.simplify the given polynomial and use it to complete the statement.the polynomial simplifies to an expression that is a blank with a blank degree of blank .

An objects motion is described by the equation d= 4sin (pi t) what will the height of the object be at 1.75 seconds?