Question

sinx-sin3x+sin5x-sin 7x
= cot 2x
cosx-cos3x-cos5x+cos 7
​

Answer 1

Answer:

Answer

cosx−cos3x−cos5x+cos7x

sinx−sin3x+sin5x−sin7x

=

(cosx−cos3x)−(cosx−cos7x)

(sinx−sin3x)+(sin5x−sin7x)

=

2sin2xsinx−2sin6xsinx

2cos2xsin(−x)+2cos6xsin(−x)

2sinx[sin2x−sin6x]

−2sin(x)[cos2+cos6x]

2cos4(x)sin(−2x)

−2cos4(x)cos2x

=cot(2x)