Question

Show that
sin(θ+π)+sin(θ-π)=-2sinθ
is this the first step?
sinθcosπ+cosθsinπ+sinθcosπ-cosθsinπ
and am i left with 2sinθcosπ?

Answer 1

yes, u are right
now, u knowed that cos(pi)=-1 right ?
so, 2sinθ(-1) = -2sinθ right ?

Answer 2

wtf??? cos(pi) is -1? omg i din knew that what a waste of 4marks T_T

Answer 3

pi is the special degrees in trigonometry, u must know that :p

Answer 4

is there a website for this? radEn?