What you’ll learn
Find missing side using trig.
Key idea
Use the supplied trig ratio with the numerator and denominator side roles intact.
Identify which side is unknown before choosing whether to multiply or divide.
Worked example
Enter the exact value or ordered values in the format requested below.
In a right triangle at acute theta, sin(theta)=4/5 and hypotenuse=15 cm. Compute the opposite leg in centimeters.
- sin(theta)=opposite/hypotenuse, so x/15=4/5.
- x=15*4/5=12 cm.
Answer: 12
Quick Check
Evaluate a worked attempt at find missing side using trig, identify the first invalid step, and provide the correction.
At acute theta, cos(theta)=5/13 and hypotenuse=26 cm. Step 1: let the adjacent leg be x and write x/26=5/13. Step 2: divide 26 by 5/13 and get x=338/5. Locate and repair the first invalid step.