If 13 sin x + 5= 0 and x є (0º; 270º) calculate the sum of 2x

Answer 1

13sinx = -5
sinx = -5/13
but from you domain, x must be in III
by Pythagoras x^2 + 5^2 = 13^2
x = ± 12 , but in III x = -12

so cosx = -12/13

I don't quite understand what you meant by
"sum of 2x"
x would be appr. 202.62

did you mean "find the sin 2x ??
then
sin 2x = 2sinxcosx = 2(-5/13)(-12/13) = 120/169