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Given sin = 4/5, use the pythagorean Theorem to find the value of cos

User Gented
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You have that sin x = 4/5, which means that the hypotenuse of a triangle is 5 and the opposite side to x has a length of 4.

By using the Pythagorean Theorem you have:

h² = c1² + c2²

where h = 5 and c1 = 4. Solve the previous equation for c1:

c2² = h² - c1²

c2² = 5² - 4²

c2² = 25 - 16

c2² = 9

c2 = 3

next, take into account that cos x is given by the quotient of the adjacent side c2 over the hypotenuse h:

cos x = c2/h = 3/5

Hence, cos x = 3/5

User Maxim Toyberman
by
6.7k points
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