'O' is the centre of the inscribed circle in a 30°-60°-90° triangle ABC with right angled at C. If the circle is tangent to AB at D then the angle COD is?
Dear Student,
Please find below the solution to the asked query:
From given information we form our diagram , As :
Here , tangent BC and AC meet radius at E and F respectively .
We know : A tangent to a circle is perpendicular to the radius at the point of tangency. So
ODA = ODB = OEB = OEC = OFA = OFC = 90 --- ( 1 )
From angle sum property in quadrilateral ADOF we get
ODA + OFA + DAF + DOF = 360 , Now substitute values from equation 1 and given value and get
90 + 90 + 30 + DOF = 360
DOF = 150 ---- ( 2 )
In quadrilateral CEOF
OEC = OFC = ACB = 90 , From equation 1 and given angle C at right angle . ---- ( 3 )
From angle sum property in quadrilateral CEOF we get
OEC + OFC + ACB + EOF = 360 , Now substitute values from equation 3 and get
90 + 90 + 90 + EOF = 360
EOF = 90 and OF = OE ( Radius of circle ) Hence
CEOF is a square and we know diagonals of square bisect the angles of square , So
COF = COE = 45
And
DOF + COF + COD = 360 ( Sum of angles on a point )
150 + 45 + COD = 360
COD = 165 ( Ans )
Hope this information will clear your doubts about topic.
If you have any more doubts just ask here on the forum and our experts will try to help you out as soon as possible.
Regards
Please find below the solution to the asked query:
From given information we form our diagram , As :
Here , tangent BC and AC meet radius at E and F respectively .
We know : A tangent to a circle is perpendicular to the radius at the point of tangency. So
ODA = ODB = OEB = OEC = OFA = OFC = 90 --- ( 1 )
From angle sum property in quadrilateral ADOF we get
ODA + OFA + DAF + DOF = 360 , Now substitute values from equation 1 and given value and get
90 + 90 + 30 + DOF = 360
DOF = 150 ---- ( 2 )
In quadrilateral CEOF
OEC = OFC = ACB = 90 , From equation 1 and given angle C at right angle . ---- ( 3 )
From angle sum property in quadrilateral CEOF we get
OEC + OFC + ACB + EOF = 360 , Now substitute values from equation 3 and get
90 + 90 + 90 + EOF = 360
EOF = 90 and OF = OE ( Radius of circle ) Hence
CEOF is a square and we know diagonals of square bisect the angles of square , So
COF = COE = 45
And
DOF + COF + COD = 360 ( Sum of angles on a point )
150 + 45 + COD = 360
COD = 165 ( Ans )
Hope this information will clear your doubts about topic.
If you have any more doubts just ask here on the forum and our experts will try to help you out as soon as possible.
Regards