• Support PF! Buy your school textbooks, materials and every day products Here!

Trig triangle problem

  • Thread starter crazy_v
  • Start date
  • #1
2
0

Homework Statement



Use the given triangle to prove that for 0 < X <90, 1 + tan^2X = 1 / cos^2X

(the given triangle is right angled with angle X marked. The hypotenuse is labeled c, adjacent angle is labeled a and the opposite angle is labeled b)

The Attempt at a Solution



I have no idea where to begin,
tanX = b/a
cosX = a/c
 

Answers and Replies

  • #2
tiny-tim
Science Advisor
Homework Helper
25,832
249
Welcome to PF!

Hi crazy_v! Welcome to PF! :wink:
Use the given triangle to prove that for 0 < X <90, 1 + tan^2X = 1 / cos^2X

tanX = b/a
cosX = a/c
But you're there

just put b/a and a/c into the original equation, and you have … ? :smile:
 
  • #3
Cyosis
Homework Helper
1,495
0
Since [tex]\cos \theta=\frac{a}{c} \Rightarrow \cos^2 \theta=\frac{a^2}{c^2}[/tex]. Write c^2 in terms of a and b now, hint Pythagoras.
 
  • #4
2
0
thanks guys

yeah that looks a lot more obvious now, thanks anyways
 

Related Threads for: Trig triangle problem

  • Last Post
Replies
6
Views
799
  • Last Post
Replies
5
Views
4K
Replies
5
Views
937
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
1
Views
2K
Replies
8
Views
8K
Replies
3
Views
774
Replies
10
Views
6K
Top