The lower right-hand corner of a long piece of paper 10 in. wide is folded over to the left-hand edge as shown. the length l of the fold depends on the angle θ. show that

l = 5/(sin(θ) cos2(θ))

What 8/12+8/11 in another way than and improper fraction

Two lines meet at a point. set up and solve an equation to find the value of x

Statements reasons 1. ab ≅ cd; ad ≅ bc 1. given 2. ac ≅ ac 2. reflexive property 3. △adc ≅ △cba 3. ? 4. ∠dac ≅ ∠bca; ∠acd ≅ ∠cab 4. cpctc 5. ∠dac and ∠bca are alt. int. ∠s; ∠acd and ∠cab are alt. int. ∠s 5. definition of alternate interior angles 6. ab ∥ cd; ad ∥ bc 6. converse of the alternate interior angles theorem 7. abcd is a parallelogram 7. definition of parallelogram what is the missing reason in step 3?