sin A , cos A , tan A
The product of all the 3 real numbers above is 0.
What is the absolute value of the sum of all these 3 numbers?
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Say A = 0 Then sin A=0 so the product of the three real numbers is 0. So s i n A + c o s A + t a n A = 0 + 1 + 0 = 1
You have only shown that the answer is "Yes" if "A=0".
Are you sure that for all A satisfying the given condition, the answer is still "Yes"?
If A = 3 6 0 k for integral k then the sum is 1, but if A = 1 8 0 + 3 6 0 k then the sum is -1
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Ahhh, that's great. I was wondering why no one reported my problem despite having 7 solvers already.
Let me fix the question now.
t a n A = c o s A s i n A
c o s A = 0 , so s i n A must be 0 . When s i n A = 0 , t a n A = 0 , so the product of these three numbers is :
s i n A × c o s A × t a n A =
0 × c o s A × 0 = 0
For what values of A is s i n A = 0 ? A = 0 , A = π
Plug them into c o s A :
c o s 0 = 1
c o s π = − 1
Because s i n A and t a n A are 0 , the sum of these three numbers is :
s i n A + c o s A + t a n A =
0 + 1 + 0 = 1
o r
0 − 1 + 0 = − 1
Thus, the absolute value of their sum is 1 .
Quite Easy! The product of the triplets ( sin A , cos A , tan A ) =0, if and only one term of the product is 0 ... Now Plugging A = 0 we get, sin 0 ∗ cos 0 ∗ tan 0 = 0 ∗ 1 ∗ 0 = 0 So, \Rightarrow (0+1+0)=\boxed{\color\red{1}}
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Firstly, note that tan A = cos A sin A , so cos A = 0 (since tan A would have an undefined value, so the product would have an indeterminate value). Thus, if we multiply the three real numbers, we get sin 2 A = 0 , so A = k π . If sin A = 0 , then tan A = 0 , and cos A = ± 1 , so the absolute value of the sum is 1 .