Question

求45°角的正切值

Answer 1

tan(∠1+∠2)=(tan∠1+tan∠2)/(1-tan∠1tan∠2)=1
tan∠1+tan∠2=1-tan∠1tan∠2
tan∠2=1/3
tan∠1+1/3=1-1/3tan∠1
4/3tan∠1=2/3
tan∠1=1/2