User interface language: English | Español

Date May 2011 Marks available 2 Reference code 11M.1.hl.TZ2.7
Level HL only Paper 1 Time zone TZ2
Command term Find Question number 7 Adapted from N/A

Question

The diagram shows a tangent, (TP) , to the circle with centre O and radius r . The size of P^OA is θ radians.

 

Find the area of triangle AOP in terms of r and θ .

[1]
a.

Find the area of triangle POT in terms of r and θ .

[2]
b.

Using your results from part (a) and part (b), show that sinθ<θ<tanθ .

[2]
c.

Markscheme

area of AOP=12r2sinθ     A1

[1 mark]

a.

TP=rtanθ     (M1)

area of POT =12r(rtanθ)

=12r2tanθ     A1

[2 marks]

b.

area of sector OAP =12r2θ     A1

area of triangle OAP < area of sector OAP < area of triangle POT     R1

12r2sinθ<12r2θ<12r2tanθ

sinθ<θ<tanθ     AG

[2 marks]

c.

Examiners report

The majority of candidates were able to find the area of Triangle AOP correctly. Most were then able to get an expression for the other triangle. In the final section, few saw the connection between the area of the sector and the relationship. 

a.

The majority of candidates were able to find the area of Triangle AOP correctly. Most were then able to get an expression for the other triangle. In the final section, few saw the connection between the area of the sector and the relationship.

b.

The majority of candidates were able to find the area of Triangle AOP correctly. Most were then able to get an expression for the other triangle. In the final section, few saw the connection between the area of the sector and the relationship. 

c.

Syllabus sections

Topic 3 - Core: Circular functions and trigonometry » 3.7 » Area of a triangle as 12absinC .

View options