Math Destroyer Practice Test #3 Question 30

[nbodah1]

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An isosceles triangle has two equal sides that are of length 5 that meet at an angle of 72 degrees. What is the length of the remaining side?


A 10sin(36)
B 5sin(72)
C 5cos(36)
D 25cos(36)
E 10sin(72)

I got 10cos(36) which is clearly not an answer. The answer is A. If you set up the isosceles triangle, it appears the missing side they are looking for would be "adjacent", not "opposite". Why is sin used in place of cos? Any clarification would help! Thanks!

 

[jaymin8]

So basically you get the base (the other side) by doing X times 2. That gives you 10sin36.

It can't be Cos because that gives you the line WE drew not the line from the original isosceles triangle.

Hope this makes sense.

Also, the angle (72) is where it is because the two equal sides of 5 meet/intersect there.