Thursday

November 20, 2014

November 20, 2014

Posted by **Alonso** on Tuesday, December 18, 2012 at 10:58am.

8. Find the exact value of sin2a if cosa = 4/5(a in Quadrant I)

13. Find the exact value of tan2 if sinB = 5/13 (B in quadrant II)

14. Solve sin 2x + sin x = 0 for 0 ≤ x ≤ 2π.

21. Write 2sin37°sin26° as a sum (or difference).

- trigonometry -
**Steve**, Tuesday, December 18, 2012 at 11:08am5.

since cot(x) < 0 in QII, 2θ is in QI

so, we have a 5-12-13 triangle in QI.

8.

we have a 3-4-5 triangle, so sina = 3/5

13.

again, a 5-12-13 in QII, so y>0 and x<0

14.

review sum-to-product formulas:

sin u + sin v = 2 sin(½(u+v)) cos(½(u−v))

21. review product-to-sum formulas:

sin A sin B = ½ cos(A−B) − ½ cos(A+B)

If you get stuck, or want to check your answers come on back.

If stuck, where do you run aground? Remember to draw the triangles where involved, paying attention to quadrants.

**Answer this Question**

**Related Questions**

Trigonometry - if cot 2θ = 5/12 with 0≤2θ≤π find cos...

trigonometry - find cos(θ)ˏsin(θ)ˏtan(θ), if cot (2&#...

trig - find cos(θ)ˏsin(θ)ˏtan(θ), if cot (2θ)=5/12...

Math - Calculus - The identity below is significant because it relates 3 ...

trigonometry - if cosθ=2/3 and tanθ<0 find the exact value sin(&#...

Trig - Given that csc θ = -4 and tan θ > 0, find the exact value of...

Trigonometry - Could someone please help me with the following q's I'm having ...

math - if cosθ=2/3 and tanθ<0 find the exact value sin(θ-5&#...

math trigono - 1. If tanθ = –√3 , what is the value of cot ? 2. ...

Pre Calculus - sec x = -2 , π ≤ x ≤ 3π Use a calculator to...