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`a,` Ta có :
`\hat{A}+\hat{B}+\hat{C}+\hat{D}=360^o`
`=> \hat{D}=360^o-80^o-80^o-100^o`
`=> \hat{D}=100^o`
`b,` Ta có :
`\hat{E}+\hat{F}+\hat{G}+\hat{H}=360^o`
`=> \hat{E}=360^o-110^o-80^o-80^o`
`=> \hat{E}=90^o`
`d,` Ta có :
`\hat{P}+\hat{Q}+\hat{T}+\hat{S}=360^o`
`=> \hat{Q}=360^o-90^o-90^o-90^o`
`=> \hat{Q}=90^o`