If Cos(t)=-7/8 with #pi<=t<=3pi/2#, how do you find the value of cos(2t)?

Related questions

• What does it mean to find the sign of a trigonometric function and how do you find it?
• What are the reciprocal identities of trigonometric functions?
• What are the quotient identities for a trigonometric functions?
• What are the cofunction identities and reflection properties for trigonometric functions?
• What is the pythagorean identity?
• If #sec theta = 4#, how do you use the reciprocal identity to find #cos theta#?
• How do you find the domain and range of sine, cosine, and tangent?
• What quadrant does #cot 325^@# lie in and what is the sign?
• How do you use use quotient identities to explain why the tangent and cotangent function have...
• How do you show that #1+tan^2 theta = sec ^2 theta#?