Hai o to khoi hanh tu hai diem A va B di nguoc chieu nhau, van toc xe di tu A la 45km/h, van toc xe di tu B la 40km/h. Neu xe di tu B khoi hanh truoc 15p thi hai xe gap nhau o diem chinh giua quang dg AB. Tinh do dai quang dg AB

1) Cho tu giac ABCD co AB=2,5cm; AD=4cm; BD=5cm; BC=8cm; CD=10cm. CMinh ABCD la hinh thang

3) Cho tam giac ABC co AB=4cm, D thuoc AC, AD=2cm, DC=6cm. Biet goc A=100, goc B-C=20. Tinh goc ABD

Cho hinh thoi ABCD co A=45, duong cao BH=h. Tinh dien tich hinh thoi theo h

tinh dien tich hinh thang can ABCD co AB//CD, AB=b, CD=a (a>b>o) va C=D=45

Cho hinh binh hanh ABCD co AD vuong goc vs AC, M la trung diem cua AB, N la trung diem cua CD, DM va BN cat AC tai P va Q

a) DM=BN

b) AP=PQ=QC

c) Tu giac PMQN la hinh thoi

Cho tam giac ABC vuong tai A, AB<AC, duong cao AH tren BC lay diem M, ve MN vuong goc voi AC, MP vuong goc voi AB. CMinh: a) Tu giac PAMN la hinh gi ? Vi sao?

b) Goi Q la diem doi xung cua M qua N, I la diem doi xung cua A qua N. Tu giac AMIQ la hinh gi ? Vi sao?

Cho a, b, c thoa man \(\dfrac{1}{a}\)+\(\dfrac{1}{b}\)+\(\dfrac{1}{c}\)=2 va a+b+c=abc. Tinh M=\(\dfrac{1}{a}\)^2+\(\dfrac{1}{b}\)^2+\(\dfrac{1}{c}\)^2

Cho tam giac ABC co AM, BN, CD la duong cao cat nhau tai H. Tu B ve duong vuong goc vs AC, chung cat nhau tai E

a) CMinh BHCE la hinh binh hanh

b) Goi K la diem doi xung vs H qua BC. CMinh: BKEC la hinh thang can

Cho tam giac ABC can tai C ( goc C<90) tren BC lay diem D. Ve DM//AB, DN//AC (M thuoc AC, N thuoc AC). Goi E la diem doi xung cua D qua MN

a) CMinh: tam giac DNE can

b) CMinh: AMNE la hinh thang can

Cho tam giac ABC, M la diem bat ki trong tam giac ABC sao cho goc MBA= MCA. Ke MK vuong goc vs AB, MH vuong goc vs AC. Goi I la trung diem cua BC, goi P va Q la trung diem cua MB va MC

a) CMinh MPIQ la hinh binh hanh

b) CMinh IH=IK