- 18 The diagram shows triangle PQR.
Diagram NOT
accurately drawn
P
17.8 cm
360
R
26.3 cm
Calculate the length of PR.
Give your answer correct to 3 significant figures.

The length of PR is 15.8 cm

Step-by-step explanation:

We will solve the question using the cosine rule

In ΔPQR

∵ (PR)² = (PQ)² + (RQ)² - 2(PQ)(RQ)(cos∠Q)

∵ PQ = 17.8 cm

∵ RQ = 26.3 cm

∵ m∠Q = 36°

→ Substitute them in the rule above

∵ (PR)² = (17.8)² + (26.3)² - 2(17.8)(26.3)(cos36)

∴ (PR)² = 316.84 + 691.69 - 936.28(cos36)

∴ (PR)² = 251.0635685

→ Take √ for both sides

∴ PR = 15.8449856

→ Correct it to 3 significant figures

∴ PR = 15.8 cm

∴ The length of PR is 15.8 cm

c. 27 units.

step-by-step explanation:

we are told that in circle a, ∠bae ≅ ∠dae.

we can see from our given diagram that in and ;

, as these are radii of our given circle.

therefore, by sas congruence postulate.

hence, side be will be equal to side de as corresponding parts of congruent triangles are congruent. so we can set an equation to find the value of x as:

now let us substitute x=17 in the expression for the length of be.

therefore, length of be will be 27 units and option c is the correct choice.