quick question (1 Viewer)

[fullonoob]

how do i change:
[cos(k-1)@ - 2cos@cosk@ into -cos(k+1)@
it's only one step (i think) but can someone explain please
thanks

 

[Trebla]

how do i change:
[cos(k-1)@ - 2cos@cosk@ into -cos(k+1)@
it's only one step (i think) but can someone explain please
thanks

cos (k-1)@ - 2cos @cos k@
= cos k@cos @ + sin k@sin @ - 2cos @cos k@
= - cos k@cos @ + sin k@sin @
= - (cos k@cos @ - sin k@sin @)
= - cos (k@ + @)
= - cos (k+1)@

 

[fullonoob]

lols wtf i posted this when bos was stuffing up, didnt even get through, but somehow appears today wow