Will mark brainliest, given: cd is an altitude of △ abc . prove: a^2=b^2+c^2−2bc cos a? (choices are on the bottom) cd is an altitude of △ abc > given △acd and △bcd are right triangles. > a^2=(c−x)^2+h^2 > a^2=c^2−2cx+x^2+h^2 > square the binomial. b^2=x^2+h^2 > pythagorean theorem cosa=x/b > b cos a = x > multiplication property of equality a^2=c^2−2c (b cos a) +b^2 > a^2=b^2+c^2−2bc cos a > commutative properties of addition and multiplication choices: definition of cosine definition of right triangle pythagorean theorem substitution property of equality

1.3

step-by-step explanation:

3x2=6   9x+6

bring down the 6 on both sides

6+6=12

12= 9x

divide by 9

12/9 =

1.3 =x

when rotating a figure 180 degrees, imagine that you are able to take the figure and turn it clockwise or counterclockwise around a center point. to rotate a figure 180 degrees, you will need to apply the rule (x, y) → (-x, -y). start by using a coordinate grid with coordinates for each vertex of the figure. the center point of the coordinate grid is located at (0, 0), which is what you will rotate the figure around. write down the original coordinates of the shape you are going to rotate. then, apply the rule. for example, coordinate (1, 2) becomes (-1, -2). another example would be, coordinate (-4, -2) becoming (4, 2). after you change each original coordinate to the rotated coordinate, you will draw your new figure.

step-by-step explanation:

answer: bearing in mind that a rectangle has a perimeter of length + length + width + width.

step-by-step explanation:

p = perimeter

l = length

x=width

p = 2l + 2x

p = 2(l+x)     < ==== perimeter of the base of the box.