`sin^2 theta= (4xy)/(x+y)^2` is true if and only if (A) `x-y!=0` (B) `x=-y` (C) `x+y!=0` (D) `x!=0,y!=0`

If s e c^2theta=(4x y)/((x+y)^2) is true if and only if (a) x+y!=0 (b) x=y , x!=0 (c) x=y (d) x!=0,y!=0

sin^2 theta =(x+y)^2/(4xy) where x,y in R gives theta if and only if

Prove that sin^2theta=(x+y)^2/(4xy) is possible for real values of x and y only when x = y , y!=0 and x!=0 .

Consider the parabola P touching x-axis at (1,0) and y-axis (0,2). Directrix of parabola P is : (A) x-2y=0 (B) x+2y=0 (C) 2x-y=0 (D) 2x+y=0

for every point (x,y,z) on the y-axis: (A) x=0,y=0 (B) x=0,z=0 (C) y=0,z=0 (D) y!=0,x=0,z=0

The equation of tangent to hyperbola 4x^2-5y^2=20 which is parallel to x-y=2 is (a) x-y+3=0 (b) x-y+1=0 (c) x-y=0 (d) x-y-3=0

The equation of common tangent to the curves y^2 =4x and xy=2 is (A) x+2y-4=0 (B) x+2y+4=0 (C) x-2y+4=0 (D) x-2y-4=0

The equation of common tangent to the curves y^2 =4x and xy=2 is (A) x+2y-4=0 (B) x+2y+4=0 (C) x-2y+4=0 (D) x-2y-4=0

The normal at the point (1,1) on the curve 2y+x^2=3 is (A) x - y = 0 (B) x y = 0 (C) x + y +1 = 0 (D) x y = 0

A parabola touches the coordinate axes at (25/3, 0) and (0, 25/4) . Equation of directrix of parabola is : (A) x+2y=0 (B) 2x+y=0 (C) 3x+4y=0 (D) 4x+3y=0