ลอการิทึมสามัญ หมายถึง ลอการิทึมฐาน 10 เขียนแทนด้วย log10A หรือ logA
จะสามารถหาค่าของ logN ได้โดย logN = loga + n เรียก n ซึ่งเป็นจำนวนเต็มว่า ค่าคาแรคเทอริสติก (Characteristic)
เป็นการทำย้อนกลับเมื่อกำหนดค่า log N แล้วให้หาค่า N โดยเรียก N ว่า แอนติลอการิทึม ของ log N 2. Antilog(log N) = N
2. กำหนด .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... 2.2 log 0.00485 .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... 2.3 log 485000 .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... 3. กำหนด log 896 มีค่า mantissa = 0.9523 หาค่าของ 3.1 log 8.96 .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... 3.2 log 0.000896 .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... 4. กำหนด .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... 5. กำหนด Antilog 0.4082 = 2.56 หาค่าของ N .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... 5.2 logN = 0.4082-2 .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... 5.3 logN = -3.4082 .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... ..........................................................................................................................................................................................................
เช่น กำหนดให้ .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... เช่น กำหนดให้ .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... เช่น กำหนดให้ .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... เช่น หาค่าของ .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... ..........................................................................................................................................................................................................
ลอการิทึมธรรมชาติ คือ log ฐาน e เมื่อ e เป็นจำนวนอตรรกยะ และ 1. หาค่าของ ln 72 เมื่อ log 72 = 1.8573 .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... 2. หาค่าของ ln 0.324 เมื่อ Antilog 0.5105 = 3.24 .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... 3. .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... 4. .......................................................................................................................................................................................................... .......................................................................................................................................................................................................... ..........................................................................................................................................................................................................
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หาค่าของ
หาค่าของ log 1153
หาค่าของ log512
หาค่าของ log1,0245
หาค่าของ log97
เมื่อกำหนดให้ Antilog 0.7980 = 6.28 Antilog 0.3979 = 2.50 และ Antilog 0.3997 = 2.51
