As shown in the figure, M is the midpoint of the side BC of △ ABC, an bisects ∠ BAC, BN ⊥ an at point n, and ab = 10, BC = 15, Mn = 3, then the perimeter of △ ABC is () A. 38B. 39C. 40D. 41

As shown in the figure, M is the midpoint of the side BC of △ ABC, an bisects ∠ BAC, BN ⊥ an at point n, and ab = 10, BC = 15, Mn = 3, then the perimeter of △ ABC is () A. 38B. 39C. 40D. 41

As shown in the figure, lengthen BN intersection AC at point D, ∵ an bisects ≌ BAC, BN ⊥ an at point n. in RT △ anb and RT △ and, ≁ ban = ≌ Dan, ≌ anb = ≌ and, an = an, ≌ anb ≌ and (ASA), ≌ ad = AB = 10, BN = DN, that is, n is the midpoint of BD, ≁ m is the midpoint of BC on the side of △ ABC, ≁ CD = 2Mn = 6, AC = AD + CD = 10 + 6, ≌ ABC's perimeter is ab + AC + BC = 10 + (10 + 6) + 15 = 41

As shown in the figure, the vertex of square mnpq is on the edge of triangle ABC. When the edge BC = A and height ad = h satisfy what conditions, the area of square mnpq is half of the area of triangle ABC?

When a = h, the square area is half of the area of the original triangle. Let the side length of the square be X. from △ AQP ∽ ABC, XA = h − XH is obtained, and the solution is x = AHA + h. according to the meaning (AHA + H) & nbsp; 2 = 14Ah, it is reduced to (A-H) 2 = 0; that is, ad = BC,