Question

Which angle in the figure below measures 90 degrees? Explain how you know

Answer 1

Given that

`\angle\text{BKD}=70^o\text{ and }\angle\text{DKC}=20^o`

We know that

`\angle BKC=\angle BKD+\angle DKC`

`\text{ Substitute }\angle\text{BKD}=70^o\text{ and }\angle\text{DKC}=20^o,\text{ we get}`

`\angle BKC=70^o+20^o`

Adding 70 and 20, we get

`\angle BKC=90^o`

Hence the angle BKC is 90 degrees.