Skip over navigation

More Trigonometric Identities

Problems

Double and Half-Angle Formulas

Addition and Subtraction Formulas

Problem : Calculate sin(θ), cos(θ) , and tan(θ) if sin(2θ) = 2 sin(30 o )cos(30 o ) .

2 sin(30 o )cos(30 o ) = sin(2×30 o ) . θ = 30 o .sin(θ) = , cos(θ) = , and tan(θ) = .

Problem : Calculate cos(15 o ) using the fact that cos(30 o ) = .

cos(15 o ) = = .9659 .

Problem : θ is in the first quadrant, and tan(θ) = . Find the sine, cosine, and tangent of 2θ .

sin(θ) = . cos(θ) = . With these values, we can calculate sine, cosine, and tangent of 2θ . sin(2θ) = 2 sin(θ)cos(θ) 0.4283 . cos(2θ) = cos2(θ) - sin2(θ) - 0.9036 . tan(2θ) = - 0.4740 .

Problem : θ is in the third quadrant, and sin(θ) = - . Find the sine, cosine, and tangent of (θ) .

cos(θ) = - . sin( θ) = = . cos( θ) = - = - . tan( θ) = - = - 3 .

Follow Us