Question

pls say the ans.......of questions 21

Answer 1

step 1 divide figure into three parts...
$triangle \: abc \: (a) \\ triangle \: cob(b) \\ angel \: abd \:ace \: (c)$
we have divide it into three steps a,b,c...now (a)
sum is 180 and (b)sum is 180

Answer 2

Ist approach:-

since BO and CO are the bisectors of angle DCB and angle DCB respectively,

then using Exterior angle bisector property, we have

angle BOC =90° - angle BAC,

then

angle BOC=90° - 70°/2,

angle BOC=90°- 35°,

then

angle BOC =55°,





IInd approach:-

angle DBC=180°-40°=140°,

since BO is the bisector of angle DBC, then

angle OBC=70°,

also
angle ECB=70°+40°=110°,

since CO is the bisector of angle ECB, then

angle OCB=55°,

Now in ∆BOC, using angle sum property se have

70°+55°+angle BOC =180°,

125°+angle BOC=180°,

then

angle BOC=180°-125°,

angle BOC=55°