(##VPU_TTT_MAT_VII_C01_E01_008_Q01##)'
How much is `angle DCE` ? `angle D C E=90^(circ)-60^(circ)=30^(circ)`
So, how'much is `angle DCA` ?

Explanation

`angle DCA=90^(circ)+30^(circ)=120^(circ)`