Exercise 73 Page 238

Practice makes perfect

a We are asked to use the cosine ratio, so let's recall the definition.

cos θ=adjacent/hypotenuse We need the angle for which the side labeled y is adjacent.

This is the angle with measure 29^(∘).

b Let's use the measures given on the diagram and the angle we identified in Part A to set up and solve an equation for y.

cos θ=adjacent/hypotenuse

Substitute values

cos 29^(∘)=y/42

▼

Solve for y

LHS * 42=RHS* 42

42cos 29^(∘)=y

Rearrange equation

y=42cos 29^(∘)

Use a calculator

y≈ 36.73402...

Round to 2 decimal place(s)

y≈ 36.73

We found that the measure of one of the legs is y≈ 36.73 units.

4.2.1 Sine and Cosine Ratios p.232-234

4.2.2 Selecting a Trig Tool p.237-238

4.2.3 Inverse Trigonometry p.241-242

4.2.4 Trigonometric Applications p.245-247

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