令a=log3(4)则3^a=3^log3(4)=4两边取常用对数lg3^a=lg4alg3=lg4所以a=log3(4)=lg4/lg3
令log3(4)=a则4=3^alg4/lg3=lg3^a/lg3=alg3/lg3=a=log3(4)所以log3(4)=lg4/lg3
