Question

A=20°,B=25°,则(1+tanA)(1+tanB）的值是?

Answer 1

tan[a+b]=

(tan[a]+tan[b])/(1-tan[a]tan[b])

=tan[45]=1

即1-tan[a]tan[b]

=tan[a]+tan[b];

所以原式等于1+(tan[a]+tan[b])+tan[a]tan[b]=

1+(1-tan[a]tan[b])+tan[a]tan[b]

=2