Please hellp with this geometery

45 cm

Step-by-step explanation:

Δ ABC is isosceles with AC, the base thus AB = BC

Perimeter = 42 and AC = 12, thus

AB + BC = 42 - 12 = 30, hence

AB = BC = 30 ÷ 2 = 15

Δ BDC is equilateral, thus has 3 congruent sides

The sides each have a measure of 15 cm ( since BC = 15 ), thus

perimeter of Δ BDC = 3 × 15 cm = 45 cm

11.2

step-by-step explanation:

when doing tangent the tangent of the angle is equal to the opposite side from the angle over the adjacent side to the angle.

tan43 = x / 12

move 12 over by multiplying each side by 12

12tan43 = x

x = about 11.2