# Maths

posted by .

Hi, can someone give me the answer to this question:
secA-tanA=1/4. Find cosA

I got: CosA=4(1-sinA) Is my answer good?

Now multply each side by (1+sinA)
CosA(1+sinA)=4 cos^2 A
CosA=1/4 (1+sinA)

16(1-sinA)=1+sinA
15=17SinA
So you have sinA, now find Cos A from your equation you originally solved.

• Maths -

Cos A= 4(1-(15/17))

cos A= 4(12/17)

Cos A= 48/17

## Respond to this Question

 First Name School Subject Your Answer

## Similar Questions

1. ### Trig

Please help with this one. I've worked it out in so many ways and can't tell what's correct. sinA sinA ----- - ------ 1+sinA 1-sinA Which answer is correct for the problem above?
2. ### maths(trigonometry)

prove that sinA-cosA+1/sinA+cosA-1=1/secA-tanA
3. ### trig

Please help me how to do this: 1) 1 + sina*cosa / (cosa + sina)^2 = 2) sina + cosa / 1- 2sin^2a =
4. ### trig

I need to count this: a) 1-tg^2a/1+ctg^2a, when sina =2/3 b) 1-tg^2a/1-ctg^2a, when cosa= -1/3 c) tga * cos^2a, when sina + cosa=5/7 d) tg^2a + 1/sina * 1/cosa + ctg^2a, when tga + ctga =5
5. ### further mathematics

Let P=(cosA sinA) (sinA cosA) Q=(cosB sinA) (sinB cosA) show that PQ=(cosA(A-B) sin(A B)) (sinA(A B) cos(A-B))
6. ### trig

Establish the following identity: CosA/1-TanA + SinA/1-CotA = CosA-SinA
7. ### Maths, Divine International Public School

If 15Cot=8, find (1+SinA)(1-SinA)/(1+CosA)(1-CosA)
8. ### trigonometry

x×sin^3A=y , cos^3A = sinA × cosA , x×sinA= y×cosA , then prove that x^2+ y^2= 1 I have no idea
9. ### Maths

Prove that [sinA/(1-cosA)-(1-cosA)/sinA]*[cosA/(1+sinA)+(1+sinA)/cosA]=4cosecA I the second part as 2 secA
10. ### maths trignometry

Prove that. √seca+2sina/seca-2sina=Sina+cosa/sina-cosa

More Similar Questions

Post a New Question