1.sin(a+b)=1/4sin(a-b) 2.sinAcosB+sinBcosA=1/4sinAcosB-1/4sinBcosA 3.3/4sinAcosB+5/4sinBcosA=0 4.3/4sinAcosB=-5/4sinBcosA 5.sinAcosB/sinBcosA=-5/3 6..tanA/tanB=(sinA/cosA)/(sinB/cosB)=sinAcosB/sinBcosA