Question

Give triangle ABC is a right triangle, and angle A is the right angle. If sin(B)=3/5, find the cos(B).

Answer 1

Answer:

Cos B = 4/5

Step-by-step explanation:

From the question given above, the following data were obtained:

Sine B = 3/5

Cos B =?

Recall:

Sine B = Opposite / Hypothenus

Sine B = 3/5

Therefore,

Opposite = 3

Hypothenus = 5

Next, we shall determine the Adjacent. This can be obtained as follow:

Opposite = 3

Hypothenus = 5

Adjacent =?

Hypo² = Adj² + Opp²

5² = Adj² + 3²

25 = Adj² + 9

Collect like terms

Adj² = 25 – 9

Adj² = 16

Take the square root of both side

Adj = √16

Adjacent = 4

Finally, we shall determine Cos B. This can be obtained as follow:

Hypothenus = 5

Adjacent = 4

Cos B =?

Cos B = Adjacent / Hypothenus

Cos B = 4/5