A:月球
B:金星
C:水星
D:地球
-- What is this?
-- It's ______ giraffe.
①cos(-60°)=—cos60°= −12
②sin75°=sin(30°+45°)=sin30°·cos45°+cos30°·sin45°= 6+24
③sin2x=sin(x+x)=sinx·cosx+cosx·sinx=2sinx·cosx;
④sin(x-y)=sinx·cosy-cosx·siny.
可持续发展的含义为 ( )