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# C3 - Trigonometry watch

1. How the hell do I solve this question, I'm confused +rep

Given that Sinx=3/5, use an appropriate double angle formula to find the exact value of sec2x
2. (Original post by I Have No Imagination)
How the hell do I solve this question, I'm confused +rep

Given that Sinx=3/5, use an appropriate double angle formula to find the exact value of sec2x
1/cos2x=sec2x

Spoiler:
Show
cos2x=1-2sin^2(x)(you know what sin x is )
3. (Original post by rbnphlp)
1/cos2x=sec2x

Spoiler:
Show
cos2x=1-2sin^2(x)(you know what sin x is )
What??

So you're saying its 1-2sin^2(3/5)??
4. (Original post by I Have No Imagination)
What??

So you're saying its 1-2sin^2(3/5)??
it means
can you square 3/5?
5. (Original post by rbnphlp)
it means
can you square 3/5?
Ah yeah I see, cheers.

Repped.
6. (Original post by I Have No Imagination)
Ah yeah I see, cheers.

Repped.
appreciated
7. (Original post by I Have No Imagination)
What??

So you're saying its 1-2sin^2(3/5)??
You are going the right way.Just go ahead.....and calculate by the formula you mentioned.Then finally reciprocal.
8. oh i am late...it has been solved!

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