# math

posted by .

how do you solve this.prove: cos2A plus cosA divided by sin2A minus sinA equal to cos2A plus 1 divided by sinA

• math -

I think there's a typo in your equation. For example , plug in A = pi/4. You then have

(0 + 1/√2)/(1 - 1/√2) = (0+1)/(1/√2)
1/√2 *√2 /(√2 - 1) = √2
1/(√2-1) = √2
√2+1 = √2

However, if you fix the right side to read (cosA+1)/sinA

you have the left side:

(cos^2 A - sin^2 A + cosA)/(2sinAcosA - sinA)

(cos^2 A - (1 - cos^2 A) + cosA)/(2sinAcosA - sinA)

(2cos^2 A + cosA - 1)/[sinA(2cosA - 1)

(2cosA-1)(cosA - 1)/[(2cosA - 1)(sinA)]

(cosA -1)/sinA

Now if you plug in any angle, the equality holds.

## Similar Questions

1. ### Maths

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?

Given:cosA= 4/5 0(less than or equal to)A(less than of equal to)90* find sinA, sin2A, cos2A
3. ### trig

Prove: 1/cos2A+sin2A/cos2A=sinA+cosA/cosA-sinA
4. ### trig

Prove: 1/cos2A+sin2A/cos2A=sinA+cosA/cosA-sinA
5. ### further Mathematics

Let A=(cosA -sinA) (sinA cosA) show that A^2=(cos2A sin2A) (sin2A cos2A)
6. ### MathS triG

1 .If tanA=1/3 and tanB=1/7 (both A and B are acute),calculate 50sin(2A +B) 2.1Prove that sin2A+2cosA-2cos^3A/1+sinA =sin2A 2.2 for which values of A in the interval[-360;360] is the identity in 2.1 undefined?
7. ### maths Pls help trig

1 .If tanA=1/3 and tanB=1/7 (both A and B are acute),calculate 50sin(2A +B) 2.1Prove that sin2A+2cosA-2cos^3A/1+sinA =sin2A 2.2 for which values of A in the interval[-360;360] is the identity in 2.1 undefined?
8. ### trigonometry

Prove : 1 + Sin2A/ Cos2A = CosA + SinA / CosA- SinA
9. ### Math

If sinA=0.5 , what is the value of cos2A and sin2A?
10. ### Maths

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

More Similar Questions