Question

вычислить cos(п/3-a), если cosa=5/13, 0

Answer 1

sina=√(1-cos²x)=√(1-25/169)=√(144/169)=12/13
cos(π/3-a)=cosπ/3cosa+sinπ/3sina=1/2*5/13+√3/2*12/13=5/26+12√3/26=
=(5+12√3)/26