If `(cosx)/a=(cos(x+theta))/b=(cos(x+20))/c=(cos(x+3theta))/d` then `(a+c)/(b+d)` is equal to (a)`a/d` (b) `c/b` (c) `b/c` (d) `d/a`

If a sin x+b cos(x+theta)+b cos(x-theta)=d, then the minimum value of |cos theta| is equal to

If (costheta+cos2theta)^3=cos^3theta+cos^3 2theta, then the least positive value of theta is equal to pi/6 (b) pi/4 (c) pi/3 (d) pi/2

Let (sin(theta-alpha))/("sin"(theta-beta))=a/b a n d(cos(theta-alpha))/("cos"(theta-beta))=c /d t h e n(a c+b d)/(a d+b c)= (a) cos(alpha-beta) (b) sin(alpha-beta) (c) sin(alpha+beta) (d) none of these

If x_1 and x_2 are two distinct roots of the equation acosx+bsinx=c , then tan((x_1+x_2)/2) is equal to (a) a/b (b) b/a (c) c/a (d) a/c

If asinx+bcos(x+theta)+bcos(x-theta)=d , then the minimum value of |costheta| is equal to (a) 1/(2|b|)sqrt(d^2-a^2) (b) 1/(2|a|)sqrt(d^2-a^2) (c) 1/(2|d|)sqrt(d^2-a^2) (d) none of these

("lim")_(n->oo)sum_(x=1)^(20)cos^(2n)(x-10) is equal to (a) 0 (b) 1 (c) 19 (d) 20

If a, b, c, d are in G.P., then (a + b + c + d)^(2) is equal to

If tanx=b/a , then sqrt((a+b)/(a-b))+sqrt((a-b)/(a+b)) is equal to (a) 2sinx//sqrt(sin2x) (b) 2cosx//sqrt(cos2x) (c) 2cosx//sqrt(sin2x) (d) 2sinx//sqrt(cos2x)

With usual notations, in triangle A B C ,acos(B-C)+bcos(C-A)+c"cos"(A-B) is equal to(a) (a b c)/R^2 (b) (a b c)/(4R^2) (c) (4a b c)/(R^2) (d) (a b c)/(2R^2)