Question

4. In triangle PQR, Q = 90°, cos R = 0.6 and PQ = 8 cm. Find PR and RQ. (May draw the own diagram by above info provided)​

Answer 1

PR = 10

RQ = 6

Explanation:

We have cos R = 0.6

also, cos R = adjacent/ hypotenuse

= RQ/PR

⇒ RQ/PR = 0.6

⇒ RQ = 0.6 PR -eq(1)

By pythagoras theorem,

PQ² + RQ² = PR²

given PQ = 8 and sub the value of RQ from eq(1):

8² + (0.6 PR)² = PR²

⇒ 64 + 0.36PR² = PR²

⇒ (1-0.36)PR² = 64

⇒ 0.64 PR² = 64

⇒ PR² = 64/0.64

⇒ PR² = 100

⇒ PR = 10

sub PR in eq(1):

RQ = 0.6*10

⇒ RQ = 6