化简：(1/sin^2(x))+(1/cos^2(x))等于A.4/sin2XB.2/sin2xC.2/sin2^(2x)D.4/sin2^(2x)

Question

化简：(1/sin^2(x))+ (1/cos^2(x))等于
A.4/sin2X
B.2/sin2x
C.2/sin2^(2x)
D.4/sin2^(2x)

Answer 1

原式=1/sin²x+1/cos²x
=(cos²x+sin²x)/(sin²x*cos²x)
=1/(sin²x*cos²x)
=4/(2sinx*cosx)²
=4/sin²(2x)
故应当选择答案D.4/sin2^(2x)