Answer:
See Below.
Step-by-step explanation:
Problem A)
We have:
When in doubt, convert all reciprocal trig functions and tangent into terms of sine and cosine.
So, let cscθ = 1/sinθ and tanθ = sinθ/cosθ. Hence:
Cancel:
Let 1/cosθ = secθ:
From the Pythagorean Identity, we know that tan²θ + 1 = sec²θ. Hence, sec²θ - 1 = tan²θ:
Problem B)
We have:
Factor out a sine:
From the Pythagorean Identity, sin²θ + cos²θ = 1. Hence, sin²θ = 1 - cos²θ:
Distribute:
Problem C)
We have:
Recall that cos2θ = cos²θ - sin²θ and that sin2θ = 2sinθcosθ. Hence:
From the Pythagorean Identity, sin²θ + cos²θ = 1 so cos²θ = 1 - sin²θ:
Cancel:
By definition:
