化简sin^2(42°+b)-2tan(45°+b)tan(45°-b)+sin^2(48°-b)-cot^2(270°-b)

化简sin^2(42°+b)-2tan(45°+b)tan(45°-b)+sin^2(48°-b)-cot^2(270°-b) 因为 tan^2b=sin^2b/1-sin^2b 所以sin^2b=tan^2b/1+ tan^2b 为什么sin^2b=tan^2b/1+ tan^2b? tan a +tan b=-4 ,tan a tan b=-7,求sin^2(a+b)+4sin(a+b)-cos ^2 (a+b)的值. 化简cos^2(-α)-[tan(360°+α)/sin(-α)] 化简:sin^2(42°+α)-2tan(25°+α)tan(65°-α)+sin^2(48°-α)-cot^2(990°-α) 化简sin^2(a+35°)+tan(315°-b)*cot(b+45°)+cos^2(145°-a) sin^2b=tan^2b/1+tan^2b tan a=3tan(a+b),b=pai/6求sin(2a+b) 已知 tan a =1 3sin(a+b)=sin(2a+b) ,求 tan(a+b) 的 值. 已知sin（2a+b）=3sin（b） 求tan（a+b）/tan(a)的值 已知sin(A+B)=3/5,sin(A-B)=1/5,证明：tan A=2tan B. 若tan^2 a=2tan^2 b+1,则cos2a+sin^ b=? 已知tan(a+b)=2tan a 证明 3sinb=sin(2a+b) 已知sin(A+B)=2/3,sin(A-B)=3/4,求(tan(a+b)-tana-tanb)/(tan^2b*tan(a+b))帮下忙 已知sin(a+b)=2/3,sin(a-b)=3/4,求[tan(a+b）-tana-tanb]/tan²b*tan(a+b)的值 化简(sin^2a-tan^2a)*(sin^2a*tan^2a) 化简：(sin^2α-tan^2α)/(sin^2α·tan^2α) 求解 已知 sin(a+b)=1/2 ,sin(a_b)=1/3,求证:tan a=5tan b求解:已知 sin(a+b)=1/2 ,sin(a_b)=1/3,求证:tan a=5tan b