1
sinα=-3/5
cosα=±√(1-sin²α)=±4/5
tanα=sinα/cosα=±3/4
2
cos²x+sin²x=1
cos²x=1-sin²x
cosx/(1-sinx)=(1+sinx)/cosx
3
(a+kb)(a-kb)
=|a|²-k²|b|²
=9-16k=0
k=9/16
1
sinα=-3/5
cosα=±√(1-sin²α)=±4/5
tanα=sinα/cosα=±3/4
2
cos²x+sin²x=1
cos²x=1-sin²x
cosx/(1-sinx)=(1+sinx)/cosx
3
(a+kb)(a-kb)
=|a|²-k²|b|²
=9-16k=0
k=9/16