sin(-15º)cos75º + cos15ºsin75º=

sin(-15)cos(60+15)+cos15sin(60+15)=

cos15(sin60cos15+cos60sin15)-sin15(cos60cos15-sin60sin15)=

sin60(cos15)^2+cos60cos15sin15-cos60cos15sin15+sin60(sin15)^2=

sin60((cos15)^2+(sin15)^2)+cos60(cos15sin15-cos15sin15)=

sin60=

(корень из 3)/2