Question

Use the diagram to answer the question

What is the measure of Enter the correct value rounded to one decimal place
( Inverse Trigonometry)

Answer 1

Answer: 36.9 degrees

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Step-by-step explanation:

With angle R as the reference angle, side RT = 8 is the adjacent side. The hypotenuse is RS = 10.

Use the cosine rule

cos(angle) = adjacent/hypotenuse

cos(R) = 8/10

cos(R) = 0.8

Now apply the arccosine function to both sides. Make sure your calculator is in degree mode.

cos(R) = 0.8

arccos( cos(R) ) = arccos(0.8)

R = 36.869897645844

R = 36.9

Note: on your calculator, you may see a button labeled
`\cos^(-1)` which is another way of expressing the notation of the arccosine function. Another term for "arccosine" is "inverse cosine".