In `DeltaRST`, `/_S=90^(@)`. `/_T=30^(@)`, `RT=12cm`, then find `RS` and `ST`.

Explanation

In `DeltaRST`,
`/_RST+/_SRT+/_RTS=180^(@)` …….(Sum of the angles of a triangle is `180^(@)`)
`:.90^(@)+/_SRT+30^(@)=180^(@)`
`:./_SRT+120^(@)=180^(@)`
`:. /_SRT=180^(@)-120^(@)`
`:./_SRT=60^(@)`
`:.DeltaSRT` is a `30^(@)-60^(@)-90^(@)` triangle.
`:.` by `30^(@)-60^(@)-90^(@)` triangle theorem,
`RS=(1)/(2)RT`.......(Side opposite to `30^(@)`)
`:.RS=(1)/(2)xx12`
`:.Rs=6cm`
`ST=(sqrt(3))/(2)RT`........(side opposite to `60^(@)`)
`:.ST=(sqrt(3))/(2)xx12`
`:.ST=6sqrt(3)cm`.