Cho tam giác ABC cân tại A, có góc A nhọn. Vẽ tia phân giác của góc BAC cắt BC tại K. a, Chứng minh tam giác ABK = tam giác ACK
b, Vẽ trung tuyến BM của tam giác ABC cắt AK tại G. Chứng minh G là trọng tâm của tam giác.
c, Cho AB= 19cm, BC= 12cm, tính đọ dài đoạn AG.

Expresa commuter train leaves downtown sation and travels at a average speed of 55 miles per hour towards the north side sation, which is 50miles away. thirty minutes later, express commuter train #7 leaves north side and travels at a average speed of 35miles per hour towards downtown sation. at the moment the two trains pass each other, how far(in miles) is train #12 from the downtown sation and how long(in minutes) has the #12 train been traveling

Write a function for a rotation 90 degrees counter clockwise about the origin, point 0

Suppose that sahil knows that 45 people with ages of 18 to 29 voted. without using a calculator, he quickly says then 135 people with ages of 30to 49 voted. is he correct? how might sohil have come up with his answer so quickly?