Bài 5:
Kẻ `CK` // `AB`
=> `CK` // `AB` // `DE`
Ta có:
+) `\hat{BAC}` + `\hat{ACK}` = `180^@` (2 góc trong cùng phía)
<=> `120 +` `\hat{ACK}` = `180^@`
<=> `\hat{ACK}` = `180^@` - `120^@` = `60^@`
+) `\hat{KCD}` + `\hat{CDE}` = `180^@` (2 góc trong cùng phía)
<=> `\hat{KCD}` + `100^@` = `180^@`
<=> `\hat{KCD}` = `180^@` - `100^@` = `80^@`
Lại có: `\hat{ACK}` + `\hat{KCD}` = `\hat{ACD}`
=> `\hat{ACD}` = `60^@` + `80^@` = `140^@`
Bài 6:
Kẻ `CK` // `AB`
=> `CK` // `AB` // `DE`
Ta có:
+) `\hat{BAC}` = `\hat{ACK}` (2 góc so le trong)
=> `\hat{ACK}` = `50^@`
+) `\hat{KCD}` = `\hat{CDE}` (2 góc so le trong)
=> `\hat{KCD}` = `60^@`
Lại có: `\hat{ACD}` = `\hat{ACK}` + `\hat{KCD}`
=> `\hat{ACD}` = `50^@` + `60^@` = `110^@`
