# Using the sine and cosine tables, and if needed a calculator, do these problems.A circle is to be drawn, passing through the ends of a line, 5 centimetres long; and the angle on the circle on one side of the line should be 80°. What should be the radius of the circle? Let AB = 5 cm and BAC = 80°.

Now Let O be a midpoint of AB.

With O as centre and radius OA = OB,

Construct a circumcircle for Δ ABC.

We know that,

In circle, The angle formed by the diameter on its circumference

is always equal to 90° .

ABC = 90° ( AC is a diameter of circle O)

AC = AO + OC = r + r = 2r

In Δ ABC, AB = AC × cos 80° (From table, cos 80° = 0.173) AC = 2r r = 14.45 cm

Radius of a circle is 14.45 cm

Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Related Videos  Champ Quiz | Trigger on Trigonometry47 mins  Basics of TrigonometryFREE Class  NCERT | Imp. Qs. Discussion - Trigonometry44 mins  NCERT | Imp. Qs. on Trigonometry42 mins  Quiz | Trail of Mixed Questions on Trigonometry59 mins  Champ Quiz | NTSE Trigonometry50 mins  Testing the T- Ratios of Specified Angles57 mins  Foundation | Cracking Previous Year IMO Questions59 mins  Trigonometry Basics36 mins  Smart Revision | Lets Revise Trigonometry45 mins
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation view all courses 