# Pre-Calculus

posted by .

If θ represents an angle such that sin2θ = tanθ - cos2θ, then sin θ - cosθ =

A. -√2
B. 0
C. 1
D. 2√2

What equation can I use to solve this problem?

• Pre-Calculus -

sin2A + cos2A - sinA/cosA = 0
2sinAcosA + 1 - 2sin^2 A - sinA/cosA = 0
2sinAcos^2 A + cosA - 2sin^2 A cosA - sinA = 0
2sinAcosA(cosA - coA) + (cosA - sinA) =
(cosA - sinA)(2sinAcosA + 1) = 0
cosA - sinA = 0 or ......

got it! That's all they asked for.
cosA - sinA = 0

• Pre-Calculus -

Oh...okay. Thanks for the help.

## Similar Questions

1. ### Math - Calculus

The identity below is significant because it relates 3 different kinds of products: a cross product and a dot product of 2 vectors on the left side, and the product of 2 real numbers on the right side. Prove the identity below. | a …
2. ### math

if cosθ=2/3 and tanθ<0 find the exact value sin(θ-5π/3) sin2θ cos2θ cos(θ/2) can some1 please help me?
3. ### trigonometry

if cosθ=2/3 and tanθ<0 find the exact value sin(θ-5π/3) sin2θ cos2θ cos(θ/2) can some1 please help me?
4. ### Trigonometry

Which of the following is equivalent to 1 − cos 2 θ/cos 2 θ?
5. ### math trigono

1. If tanθ = –√3 , what is the value of cot ?
6. ### trig

An object Is propelled upward at an angle θ, 45° < θ<90°, to the horizontal with an initial velocity of (Vo) feet per second from the base of a plane that makes an angle of 45° with the horizontal. If air resistance …
7. ### Math (Trigonometry)

θ is an acute angle such that tan(θ) = 12. What is the value of 5√5⋅(sinθ+cosθ)?
8. ### Trigonometry

There are four complex fourth roots to the number 4−4√3i. These can be expressed in polar form as z1=r1(cosθ1+isinθ1) z2=r2(cosθ2+isinθ2) z3=r3(cosθ3+isinθ3) z4=r4(cosθ4+isinθ4), …
9. ### Math (Trigonometry)

θ is an acute angle such that tan(θ)=1/4. What is the value of 17√17*(sinθ+cosθ)?
10. ### Precalc/Trig

Sorry there are quite a few problems, but I just need to know if these are correct (and if they aren't, where I went wrong): 1. Solve these equations. tanθ = -√3 θ = 2π/3 + kπ θ = 5π/3 + kπ …

More Similar Questions