Hi

Not exactly

sinē x + sin x = cosē x

sinē x + sin x = 1 - sinē x

2 sinē x + sin x - 1 = 0

which is a quadratic in sin x

sin x = -1 or sin x = 1/2

x = 3pi/2 or x = pi/6 or x = 5pi/6

Use sin(a+b) = sin a . cos b + sin b . cos a

with a = 2x and b = x

You can factor out cosē x

cosē x - 4 cosē x = cosē x (1-4) = -3 cosē x

It is exactly the same as -3y = y - 4y with y = cosē x