https://www.khanacademy.org/math/precalculus/x9e81a4f98389efdf:trig/x9e81a4f98389efdf:angle-addition/v/proof-angle-addition-sine 2021-05-05T14:53:16Z Proof of the sine angle addition identity Sal proves the identity sin(x+y) = sin(x)*cos(y) + cos(x)*sin(y). Sal Khan video https://cdn.kastatic.org/googleusercontent/egZR3z6x8IGAPeU5EAdzsvyL4RnjWigy9B_OnXbOh9W2mw3jSIKSig9uvNCMNyx0M0UpGJrLARgaoIfUhhq7fZI Proof of the sine angle addition identity Sal proves the identity sin(x+y) = sin(x)*cos(y) + cos(x)*sin(y). https://cdn.kastatic.org/ka-youtube-converted/R0EQg9vgbQw.mp4/R0EQg9vgbQw.mp4 506 Equivalent representations of trigonometric functions https://www.khanacademy.org/math/precalculus/x9e81a4f98389efdf:trig/x9e81a4f98389efdf:angle-addition/v/proof-angle-addition-cosine 2021-05-05T14:53:19Z Proof of the cosine angle addition identity Sal proves the identity cos(x+y) = cos(x)*cos(y) - sin(x)*sin(y). Sal Khan video https://cdn.kastatic.org/googleusercontent/FasP1nWHi_ADiQthXb5kLHxdJw2ww_abdrkLF2zuHo7X1r1TOAfd37BLg1JOjGdEEn4-K8Bde1hl2aYF_vZzn6Zb Proof of the cosine angle addition identity Sal proves the identity cos(x+y) = cos(x)*cos(y) - sin(x)*sin(y). https://cdn.kastatic.org/ka-youtube-converted/0VBQnR2h8XM.mp4/0VBQnR2h8XM.mp4 362 Equivalent representations of trigonometric functions https://www.khanacademy.org/math/precalculus/x9e81a4f98389efdf:trig/x9e81a4f98389efdf:angle-addition/v/trigonometry-identity-review-fun 2021-05-05T14:53:24Z Trig angle addition identities Sal reviews 6 related trigonometric angle addition identities: sin(a+b), sin(a-c), cos(a+b), cos(a-b), cos(2a), and sin(2a). Sal Khan video https://cdn.kastatic.org/googleusercontent/q779WlSevH6c0FCkG6uJcgjnP-3oXG6igoQNkUMmaUC_iYs2ef5ZtpHgGVMziteKMOmz7gjlpqZzF16rq8z2hxo Trig angle addition identities Sal reviews 6 related trigonometric angle addition identities: sin(a+b), sin(a-c), cos(a+b), cos(a-b), cos(2a), and sin(2a). https://cdn.kastatic.org/ka-youtube-converted/a70-dYvDJZY.mp4/a70-dYvDJZY.mp4 667 Equivalent representations of trigonometric functions https://www.khanacademy.org/math/precalculus/x9e81a4f98389efdf:trig/x9e81a4f98389efdf:angle-addition/e/trig_addition_identities 2026-06-09T17:40:46.212160686Z Use the trig angle addition identities Find the trig values of sums of angles whose individual trig values are known. Mark Wittels exercise https://www.khanacademy.org/math/precalculus/x9e81a4f98389efdf:trig/x9e81a4f98389efdf:using-trig-id/e/applying-angle-addition-formulas 2021-06-05T02:06:08Z Find trig values using angle addition identities Find the trigonometric values of various angles that (while they are not special angles) can be expressed as the sum or difference of special angles and vice versa. Tomer Gal exercise https://www.khanacademy.org/math/precalculus/x9e81a4f98389efdf:trig/x9e81a4f98389efdf:sinus-models/v/inverse-trig-with-model 2021-02-11T09:29:38Z Trig word problem: solving for temperature Sal solves a word problem about the annual change in temperature by solving a sinusoidal equation. Sal Khan video https://cdn.kastatic.org/googleusercontent/JTD7xAQhddgrOwp5w5YKUktQrbIe2MYReevXy5pg5wT7dc9-UA50Hp-I9f8Brc6pENZI7QFr8eOuC5TJNvgg-lBP Trig word problem: solving for temperature Sal solves a word problem about the annual change in temperature by solving a sinusoidal equation. https://cdn.kastatic.org/ka-youtube-converted/2pwnr_soZEU.mp4/2pwnr_soZEU.mp4 503 Equivalent representations of trigonometric functions https://www.khanacademy.org/math/algebra2/x2ec2f6f830c9fb89:trig/x2ec2f6f830c9fb89:sinusoidal-models/v/modeling-periodic-function-with-shift 2021-06-29T20:27:58Z Trig word problem: length of day (phase shift) Sal solves a word problem about the annual change in the length of day by modeling it with a sinusoidal function that has a phase shift. Sal Khan video https://cdn.kastatic.org/googleusercontent/aMADOSFBMAAQP10PZBxzr2pgzbZF_RVf22IpA0-9upx1scxKi87hJ23lGktb_2yFyyXmb5x2Ts-JSINnytwP2peqcA Trig word problem: length of day (phase shift) Sal solves a word problem about the annual change in the length of day by modeling it with a sinusoidal function that has a phase shift. https://cdn.kastatic.org/ka-youtube-converted/MJBjGnR6vlk.mp4/MJBjGnR6vlk.mp4 463 Equivalent representations of trigonometric functions https://www.khanacademy.org/math/precalculus/x9e81a4f98389efdf:trig/x9e81a4f98389efdf:sinus-models/e/inverse-trig-word-problems 2026-05-05T18:10:50.367167117Z Sinusoidal models word problems Solve word problems that involve real-world contexts that are modeled by sinusoidal functions. Tomer Gal exercise