a*sin(pi/4 - x) - b*cos(pi/4 - x) = a*sin(pi/4 + x) - b*cos(pi/4 + x) 怎么得到（a + b）* sinx = 0

a*sin(pi/4 - x) - b*cos(pi/4 - x) = a*sin(pi/4 + x) - b*cos(pi/4 + x) 怎么得到（a + b）* sinx = 0 a,b∈（3pi/4,pi）,sin(a+b)=-3/5,sin(b-pi/4)=12/13,则cos（a+pi/4）= 已知a,b,属于（3pi/4,pi),sin(a+b)=-3/5,sin(b-pi/4)=12/13,则cos(a+pi/4)=? cos(pi/4-a)=3/5 sin(3pi/4+b)=5/13 求sin(a+b) 方程sin pi x =(1÷4)x的解的个数是 A.5 B.6 C.7 D.8 pi指圆周率 用matlab解方程组,x,y为已知列向量,求a,bx = 500*sin(a*pi/180)+400*sin((a+b)*pi/180)y = 500*cos(a*pi/180)+400*cos((a+b)*pi/180) cos(pi/4-a)=1/7,sin(3pi/4+b)=11/14cos(pi/4-a)=1/7sin(3pi/4+b)=11/14 pi/4 若F(X)=ASIN(X+PI/4)+3SIN(X—PI/4)是偶函数,则A= 已知x属于[0,pi],则函数y=2sin(pi/6-2x)为增函数的区间是a.[0,pi/3] b.[5pi/6,pi] MATLAB编程 求大侠改错a=-pi:pi/50:pi;b=pi:pi/50:4*pi;x=1:0.1:8;subplot(1,3,1),plot(a,a.*cos(a))xlabel('x'),ylabel('y'),title('y=xcosx')subplot(1,3,2),plot(b,b.*tan(1/b).*sin(b.^3))gtext('y=xtanxsinx '),axis([3 13 0 100])subplot(1,3,3),plot(x,ex y=0.75sin(x+Pi/4) ( x属于[-pi,pi])的减区间 已知f(x)连续可导,证明g((x,y),(a,b))亦连续.已知f(x)在(-pi/2,pi/2)上连续可导,定义g(x,y)在集合E:=(-pi/2,pi/2)*(-pi/2,pi/2),g(x,y)=[f(x)-f(y)]/[sin(x)-sin(y)],证明g(x,y)在E上连续. 若a、b为实数,且关于x的一元二次方程x^2-ax+b=0的两个实数根伟sin@和cos@(-pi/4 sin(PI/2+a)=-4/5 a属于(Pi,3pi/2)则cos(Pi/3-a)为 lim x-> 1 (ax^4 + bx^3 + 1)/[(x-1)(sin (pi x)],a,b是常数,极限存在且为有限,问LIM是多少? sin(pi/4+2a)sin(pi/3-2a)=1/4,a属于(pi/4,pi/2),求2sin^2a+tana-cota-1 matlab surf画三维图的问题n=4;c=3e8;f=30e6;lamda=c/f;beta=2*pi/lamda;d=0.5*lamda;alpha=0;a=linspace(0,2*pi);b=linspace(0,pi);psi=beta*d*cos(a)+alpha;Fa=abs(sin(n*psi/2)./(n*sin(psi/2)));z=Fa.*cos(a)；x=(Fa.*sin(a)).*cos(b);y=(Fa.*sin(a)).*sin( tanθ=a,求[sin(pi/4+θ)/sin(pi/2-θ)]*tan2θ