Difference between revisions of "1999 AHSME Problems/Problem 15"

(Solution 2 (Alternate))
(Solution 2 (Alternate, Slightly Longer))
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==Solution 2 (Alternate, Slightly Longer)==
 
==Solution 2 (Alternate, Slightly Longer)==
Note that <math>\sec x - \tan x = (1-\sin x)/\cos x</math> and <math>\sec x + \tan x = (1+\sin x)/\cos x</math>. Let <math>(1+\sin x)/\cos x = y</math>. Multiplying, we get <math>(1-\sin^{2}x)/\cos^{2}x = 1</math>.Then, <math>2y = 1</math>. <math>\sec x + \tan x =  
+
Note that <math>\sec x - \tan x = (1-\sin x)/\cos x</math> and <math>\sec x + \tan x = (1+\sin x)/\cos x</math>. Let <math>\sec x + \tan x = y</math>. Multiplying, we get <math>(1-\sin^{2}x)/\cos^{2}x = 1</math>.Then, <math>2y = 1</math>. <math>\sec x + \tan x =  
 
\boxed{\textbf{(E)}\ 0.5}</math>. ~songmath20   
 
\boxed{\textbf{(E)}\ 0.5}</math>. ~songmath20   
 
Edited 5.1.2023
 
Edited 5.1.2023

Revision as of 18:34, 1 May 2023

Problem

Let $x$ be a real number such that $\sec x - \tan x = 2$. Then $\sec x + \tan x =$

$\textbf{(A)}\ 0.1 \qquad  \textbf{(B)}\ 0.2 \qquad  \textbf{(C)}\ 0.3 \qquad  \textbf{(D)}\ 0.4 \qquad  \textbf{(E)}\ 0.5$

Solution 1 (Fastest)

$(\sec x - \tan x)(\sec x + \tan x) = \sec^{2} x - \tan^{2} x = 1$, so $\sec x + \tan x = \boxed{\textbf{(E)}\ 0.5}$.

Solution 2 (Alternate, Slightly Longer)

Note that $\sec x - \tan x = (1-\sin x)/\cos x$ and $\sec x + \tan x = (1+\sin x)/\cos x$. Let $\sec x + \tan x = y$. Multiplying, we get $(1-\sin^{2}x)/\cos^{2}x = 1$.Then, $2y = 1$. $\sec x + \tan x =  \boxed{\textbf{(E)}\ 0.5}$. ~songmath20 Edited 5.1.2023

See Also

1999 AHSME (ProblemsAnswer KeyResources)
Preceded by
Problem 14
Followed by
Problem 16
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